Straight Married Guy (Figleaf): Oh boy, where did I just see a link to a TV clip of a woman walking up to men who cat-called her and asked them why? (You can answer in comments if you've got the link.) Anyway, the men all acted completely embarrassed when put on the spot about it. Which, I think, actually says a lot about why men do it: not because they're actually interested in the women they cat-call. Instead (based, I'm embarrassed to say, on my own behavior as a construction worker in my teens and twenties) it's about a) letting other men you're with know you're straight - dumb, I know but there you go - and maybe calling on other men to confirm they're straight too, b) bonding with other men through "bravery" - even dumber, I know, but again there you go, and c) attempting to compliment women you find attractive but (and this goes back to item B) you're pretty sure wouldn't actually be interested in you.
Feminist analysis would probably add other things like keeping women in their places, telling women they're valued only for their sexiness, etc. But I think those are only side effects of what's really mostly male-to-male communication. Which is why I think men are embarrassed and even shocked when a woman they've cat-called tries to start a conversation. Final bit of evidence: at least in my experience, most men don't (or at least didn't) cat-call women they think they might actually have a chance of asking out later.
Gay Engaged Guy (Joel Derfner, author of Swish): Men cat-call because some atavistic impulse leads us to believe that it might get us sex. Any time a man cat-calls at you, a part of him he isn't aware of in any meaningful way is really hoping you'll immediately stop whatever you're doing, come over, knock him down, and have your way with him. It's like a mating ritual. Please understand that I'm not saying any man thinks this is actually going to happen (though there's always Dimitri the Lover, so who knows). This is all happening below the level of consciousness.Read More »from Em & Lo's Wise Guys: Why Do Men Cat-Call?