Because they are gays and attracted to masculinity. And muscled inteligent man is an archetype of male beauty since ancient Greece and even before that.
I want muscles coz I find it really hot
and I wouldn't mind if the guy I'm dating had it too, but not having it is not a turn off for me
I'm just not comfortable dating fat(ish) guys coz they seem bigger than me and I'm usually the top, it doesn't work
I honestly don't care for muscles, I find a cute lil tummy and thick body hotter than muscles. But then again my boyfriend has abs and he's toned/ has muscles so I guess it depends on the person for me. I do have a thing for nice nipples and pecs tho.