I ask a simple question to you all... why? Why are breasts considered sexual?
Because women have them, and men are naturally attracted to women, so men find breasts attractive. Mystery solved!
I mean sure, marketing over-sexualizes breasts. But it's not marketing that made breasts sexy. They already were, otherwise the marketing wouldn't work as well as it does. Think about it, if they censored the bare arms of women would arms suddenly become super sexy? No. Everyone has arms, who cares.
If men had breasts then it wouldn't be a big deal, because then breasts wouldn't be feminine.
Lets flip it around to help prove my point a bit. As a general rule, women find muscular men attractive. Why? Because during puberty, boys get stronger, their muscle-mass increases. Probably because back when the human race was young, long before we got too smart for our own good, men were running around hunting and scavenging. We needed muscles for that, and they only developed those muscles further during hunting, scavenging and so on. Therefore, muscles are masculine. See what I'm getting at?
That's my theory anyway. Media doesn't make breasts sexy, it just promotes the fact that they are.