Dude... You are overanalyzing the game too hard.
You have the option of having big tits because people kept insisting on them being added, so they got added, same for the big ass.
In the beginning, both of those didn't exist and they weren't planned (as far as i know). And also they are optional, if you keep selecting them every time you create your character, that's on you. I select them as well, because i like it that way.
When you overanalyze stuff, it stops being fun.