I think a lot of the time they like it because they don't have to worry about commitment and responsibility as much that way. If the guy's a jerk he'll be much easier to get rid of later than if he's a really nice guy. In my experience most of them that like jerks aren't worth being with anyways. I've never been a jerk, but I do come off as a mystery a lot and girls flock like flies. Most of them just want one thing (yes folks, that whole girls don't want sex as much as guys isn't exactly true), and they don't want strings attached. Some girls see all these other girls going after that type and follow suit cause they must be the best guys. Some girls don't care if the guy is a jerk, as long as he buys her lots of nice things. Some girls are umm jerks themselves and so perfectly suited. And some, I dunno why they wind up with jerks. But trust me, there are a lot of girls that like nice guys too, and usually they are by far the best of the lot. And much more capable of being loving and expressing themselves. I know I'm not covering every case here, there are some times when a girl gets trapped, and other similar things, but for the most part, from what I've observed and experienced, what I've said holds true.
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"Life is what happens while you are busy making other plans." - Lennon