Why do guys like ass?

I (27M) don't fully know what orientation I am sexually in all honesty (I think I may be ace), but one thing that always seems to confuse me, and I find it hard to picture it from other angles. Why do guys seem to always like ass? Like Its something that everyone has, it's always depicted as guys seem to like ass or tits. For me it's just "ok? It's just a butt?" Everyone has one, I see literally 0 appeal in it. Is this just me or is this something others think as well?

Edit: So after waking up and reading some comments and responding to DMS, I learned a few thjngs. I think I may be somewhere on the ace spectrum (someone suggested aegosexual and looking into it kinda feels like how I see it). On top of that it just seems to be an urge people have that people have, a mix from social conditioning and biology. I am also aware that it's a thing that guys and girls like, I'm not just saying it's a thing for guys