Americans are obsessed with making women under 100 lbs. The fuck are you talking about?
Either way, the ancient Romans/Greeks disagree with all your assessments.
Its a hard-wired thing...bigger hips/ass, better for bearing children. Big tits = more able to feed off spring. Not difficult to figure out.
Either way, would you rather fuck a skinny ass bitch from behind, with her bones sticking your pelvis, or a nice round ass that allows you to bounce off of and return fire? Sorry, but im going for the latter. Im coo off a bony ass bitch.