Why do some people like other pairings over Alpha x Omega?

Why do some people like omegaverse but prefer AxA, AxB, BxO, or OxO, over AxO in BLs?

I've seen many people express their disappointment when one of the main characters of a story turns out to be an omega instead of an alpha or a beta like they thought especially when the other main character is an alpha bcs that would mean the story is going to be about AxO.

Is it because AxO pairings are too common that it's becoming boring to some? Or are there some other reasons?

I thought omegaverse is a universe that's made up to make it possible for couples to bond their body and souls together through mating bites and for male couples to be able to get pregnant since it's impossible irl. But having AxA, AxB, BxO, or OxO couples means the purpose of writing the story in omegaverse is moot, no? (Unless the specific story itself alters the common concept of omegaverse and made it so that everyone can get pregnant, ofc. Though, if that's the case, having ABO genders would also be moot since everyone has the reproductive organs to conceive???)

Or maybe I'm misunderstanding the concept of omegaverse itself??

Anyways, I'd appreciate if some of you can share your thoughts if you do prefer other pairings over AxO. This is no way a dig at anyone's preference, btw. I'm genuinely asking out of curiosity and I want to see people's perspectives on this.