Some people enjoy the bitterness, I know I do.
However, I've gotten sick of IPAs everywhere and I share your sentiment.
A few years ago, there weren't as many craft breweries around Central New Jersey. They had a small yet varied selection - one or two different lagers, stouts, wheats, and IPAs.
Then those came around (mostly hipsters who couldn't even handle the alcohol content of one glass!) who started promoting an IPA as an "adult" drink. Now there are craft breweries - if not multiple - in damned near every town on the Shore. At many a good three quarters if not more of their offerings are some variant of an IPA.
I would guess because bitterness is what makes it taste like an "adult" drink.
A lot of non-alcoholic options tend to be sweet: soft drinks, fruit juices, mocktails being the first that come to mind.
The newer trend with companies like seedlip, or with actually good non-alcoholic beers means you can having something "adult" to drink without rotting your teeth
I would assume it comes from disliking the taste of hops. I find hoppy beers taste like soap, personally but IPAs and other hoppy beers have become incredibly popular, so navigating the craft brew landscape can be a minefield for people that dislike it.
Still, it's not like there's exactly a shortage of beers for people that don't really like hops so while it makes it kind of difficult sometimes (especially when all you're given is a name of a beer) it isn't something to get that upset over.
Because there is way more to beer than IPAs! There are lagers, hefeweizens, stouts, radlers, and yet the only beer that's stocked in any quantity are the same boring bitter-ass "craft" IPAs.
And maybe I just hate watching people and the market gravitate towards only one thing.
For a bit more detail than some of the other responses.. for example, seeing Lagunitas on the name made me concerned it would be very hop-bitter (IBU) but that was not the case at all. I found it to be more like a modern flavored sparkling water (think LaCroix and the like) except with the floral flavor of dry-hopping, and a bit of sweetness kinda like tonic water.