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Ah! Believe it or not, this is a sociology question. The big "nature vs nurture" debate.
All in all, I think you are generalizing way to much on men here--not every guy is a player. And while it seems that they might have been born to be that way, I'm a firm believer in the nurture standpoint. They got positive feedback from being a "player." They could date whomever they wanted, and get what they wanted. But this definitely isn't every guy.
The only thing under the nurture standpoint would be genetics, and I don't really think someone can be genetically inclined to be a "player." They could be prone to anxiety, or depression. Maybe they feel better about themselves when they always have a girl. Maybe it's reassuring.
Still, have hope! Not everyone is cruel!