Why do authors bait with multiple ships?

Why do authors bait with multiple ships when they have no intentions of making it a harem ending?

If there are multiple love interests there will always be people who like different pairing and not all of them are going be happy with the end game couple. Wouldn't it be better to have just one couple right from the beginning and focus on them? If the author wants to show different dynamics they can always have multiple couples instead of pairing up multiple girls/guys with one MC. Fans would be happy and it would be a win-win situation. I don't understand why authors bait with multiple ships, how does it benefit them?

no one will read it otherwise
I wouldn't have bothered to watch oregairu if I knew from the beginning that 8man will bang the ugly girl

It makes every part interested. Every shipping possible, until the very end. More audience.

I thought that it was obvious from the beginning that it would be Yukino and Hachiman, those two were the main characters, Yui kinda took a backseat and there was no other obvious girl to end up with him

But the disappointment is just as big when it seemed that two characters had mutual feelings but someone else swept away the MC like in Nisekoi, end couple was kinda obvious from the beginning but all the false hope and baiting with Onodera kinda sucked since they didn't end up together. 

I totally get you but in the end, people who will be disappointed and rage over the overall ship are fewer than the people who will just get angry then forget about it next day, it was trial and error for many years and we came to this in my opinion. Well, there are romances which focus on a single couple but let's be fair, those aren't that popular compared to the others

It allows the audience to decide which ship is best, and starts heated debates between different groups supporting different ships. The more active a fandom, the better for the author.

Wouldn't heated debates be an overall negative experience for the fans? Also there are overly zealous shippers every once in a while who send death threats to the author/anime staff when their ship starts losing.

Wouldn't harem endings or multiple routes like Fate series be better in that case?

Well for starters, I'm referring to profit. More heated debates = more people interested in the series, and more people interested in buying the manga. If a fandom is so invested in sth that they're willing to have heated debates for, it translates to a higher popularity and more profit for the franchise.

And obviously death threats are pretty common, but isn't that a general concern for every mangaka nowadays? It seems as tho even the least controversial series, are receiving a ton of toxicity from their overzealous fans. 

So if you can't win on taming the fanbase, then focus on the profit. After all, these mangakas need to survive. A simple death threat online isn't going to harm them as much as low income from their work.

In that case why don't they have a harem ending or multiple routes? All fans would be happy then and they can sell more merch with multiple pairings.

In reverse harem I believe it's to attract the female audience because of the many handsome boys and in harem it's almost the same thing but with a hint of ecchi.
It could also be to give a certain degree of mystery (even though it's obvious which girl/boy the protagonist will end up with) to attract the audience.

From my experience, multiple routes are hated by fans. It's like a cheap trick authors use when they run out of ideas.

I think in these cases the mangakas just pick whatever ship they personally enjoy the most, or sometimes they go for shock factor, which usually backfires.

As others have mentioned, it makes for a more appealing and suspenseful story, which is good for engagement and revenue. Different strokes for different folks as they say. If you have a lot of girls with varying body types and personalities, it increases the likelihood of your audience getting attached to at least one of them. The more the better till a certain point. 

Even if the final ship upsets people, that's fine, because it's right at the end. By that point, the author has already profited off the work. He or she may have to tank upset fans and maybe a few death threats, but it is what it is. Look at Nisekoi. The uncertainty of Raku's choice did a lot of heavy lifting for that manga in terms of viewership. 

Then why not have multiple couples instead of 1 MC and multiple love interests? You can have different types of girls and boys that way.

Also, one part of the fandom will rage anyway. It doesn't matter. The way to minimize it is ending with the most acceptable and obvious one.

The antithesis of what GoToubun did.

The big appeal of these shows/series is that people self-insert themselves into the MC. That's why harem/ecchi MCs are so bland. It's so that the reader/watcher can more easily insert themselves into the character and imagine themselves being approached/pursued by these various beautiful girls who love the MC (usually for the most banal reason like "he is kind")

Having multiple couples do not scratch this itch. And usually, these shows/works try to make the MC the only male character in these girl's life. Occasionally, there will be the goofy best friend and whatnot, but these anime/manga try to make it so that there are no competing males in the girls' lives.

Ultimately, the harem genre is made to appeal to lonely otaku/weebs. The key points are:

1-  There have to be a lot of girls of varying body types and personalities (not always).
2-  These girls fall in love with the MC for some basic reason.
3 - The MC has to do pretty much nothing to get the girls' love or keep it. It basically just falls in their lap. 

Are otakus huge masochists in that case since it's always the tsundere that wins in the end? Why would anyone want to be with a rude and violent girl

The final pairing is ultimately the author's choice. Don't think the popularity of the character is the deciding factor, though it's possible that the author might be influenced by polls and the like. I say this because most harem stories' end couples can be easily predicted if you look at the setups throughout the story. Nisekoi for instance: in my mind, there was no way it wouldn't be Chitoge.

Still, even if the end couple seems obvious, readers will hang on until the final verdict. Perhaps there will be a twist. I've personally never seen a drastic switch up in all my days of consuming anime/manga, though, there are a few web novels where the final pairing did surprise me.

I write myself, but I didn't care to bother with the 'who will they end up with' route, and just went with a straight harem ending. But that's just me.

I'm sure there are quite a few, but I haven't really seen that many anime where they follow just one couple. Typically it's always a harem, or if they do follow one couple there's always unnecessary love triangles thrown in. I get that it makes things spicier, but I think following one couple through the entire process (without any other love interests) can be made just as spicy.

Battle shounen authors don't. It's always pretty clear who the main love interest is, and fans end up baiting themselves and obsessing over ships that were never going to be canon.

But for the authors who do bait with multiple ships, I think it's mostly to keep the attention of fans who are only interested in a specific character, and to give them a false sense of hope up until the ending thus keeping them reading up until the ending. After all, it doesn't matter what story you're trying to tell if most of your readers lose interest half-way through and drop the series, resulting in it getting axed long before the story reaches its natural conclusion

How is it any different from stories with a revolving door of villains each of whom are portrayed as some kind of unstoppable force? We all know the hero will prevail against "insurmountable" odds and a new villain will take his place.

To create more engagement in their fandom and thus create more "wars" leading to increase in sales

To toy with the readers hearts' stringers.

I didn't know it was always the tsundere that wins (no, it isn't always) and tsunderes and just rude and violent all the time.

So you can pass off writing a terrible main ship and not lose a lot of viewers because the prospect of another girl potentially winning is there (even if that chance is close to 0%)

"More girls is better than less girls" seems like the maxim there. I still have no real opinion on that saying, even after just making it up.
The actual winner is obvious from the start in most cases, and usually isn't the actual best girl, but that's to be expected.

Authors are fucking dogshit losers who have no idea how to make a good story most of the time especially when it pertains to romance

Visual Novel creators atleast have the decency to let you FUCK every girl in their own route and also sometimes have HAREM endings 
EROGE>>>>ALL MEDIA fuuck you anime/manga authors!!