NSFW: Why do women find it sexually arousing to have their breasts touched?

Stemming from another recent question about why men love boobs, I got to thinking about them (which is fine with me). Some valid points are made about how there is an evolutionary reason, and that men are culturally bred to find them attractive in a Judeo/Christian society in which they are such “forbidden fruit.”

Since there are cultures where women go topless and men don’t appear to think of breasts as a huge deal, what is the reason women enjoy having their breasts played with? Why does playing with the nipples turn them on? Is it for the same reason men are turned on (the forbidden fruit idea)? Are women in topless cultures aroused by having their breasts touched, or is it just as exciting to them as stroking any other part of the body?