My observation is that Americans seem obsessed with size in general, and breasts in particular. Here in Australia, bare breasts at the beach, in a film, on television during normal viewing hours, are considered normal. As far as size goes, a bigger meal isn't better than a smaller one, it's the quality that counts. A smaller car is often better than a bigger one, because you can build in better handling dynamics. This is the case with many things but penis is a bit different, because longer can reach spots deep inside that shorter can't, and thicker feels different than average-sized.
As far as average-sized breasts go, there are advantages, especially as a woman ages.