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okay, let me break it down...
there is a reason that men like breasts. it has to do with Evolution. you know, the thing that determines most of who you are and what you're capable of.
anyways, babies are what makes the world go round. babies need food. boobs feed babies. women have boobs. women have babies. women need sperm in order to have babies. men have sperm. men need to give sperm to women. men need to care enough about giving sperm to women. yadda yadda yadda.
the humans that survived are the ones that had ancestors of men who were attracted enough to things with boobs (women, boobs are essential for reproduction) that they gave them their sperm.
of course that's only a teeny teeny part of the story, but it is a substantial reasons why men like boobs and we can never explain why.
what you originally said is like saying "why do men like butts? they're just flesh. so is steak. hell, why do men even like women in the first place?"
the attraction that men and women have for each other can be explained rather easily wrt Evolution. that's not the only reason, though, but easily the biggest.