Because they are beautiful. There is a long scientific reason for this, but basically it has to do with sexual attraction.
No, I prefer B-cup girls.
Men like nude girls because it might give them the "Sexual Excitement" that most men enjoy. and girls look better because men like boobs and butts
gay men arnt interested in dating girls
same reason men have penises and women dont, men are attracted to boobs, women are attracted to penises.
That normally doesn't require any extraordinary effort. Men will normally be interested in boobs, but may try not to make it too obvious, so as not to seem rude.
The men don't need them.
Many men feel the gluteus maximus or buttocks would be the sexiest body part.
that depend on the boobs of her mother, grandmother... if they have big boobs is most likely that the girl could have big boobs
sometimes when a girl is talking about "the girls" it means her boobs.
They're embarrassed because if they know other girls have bigger boobs than them, they feel like the girls that have bigger boobs are better and more attractive than them. If that's not the case, then maybe they think their boobs are too big. I don't know... You shouldn't be embarrassed about how big your boobs are. 
They are could boobs boobs are awesome boys like you for them.
ask them nicely ;)