For some reason, our society is fascinated with, "Big". Large breasts are more noticable, and guys go by societies rules.
In other countries, Italy for example, small breasts are considered very attractive. In other countries, breast size is not much noticed as long as they do the job for which they were intended. (Suckling babies).
In addition to myself, I know a number of guys who clearly do not prefer large boobs!
We can grow big breasts by doing sex with other boys because they suck our breasts.
To feed babies and attract men.
BIG
as big as God intends
As Big as E
Big.
Big breasts are 'des gros seins' (familiar/slangish) in French.
Genetics.
It varies!
A cup
I guess that depends on how big your breasts are....?
Really big