because they where available to them, older to their own age girls are always uptight and dont want anyone, or they (older girls) were stupid enough to of let themselves be used by other guys, most guys like the pure innocent girls, and for many guys we dont always get to have a girl when we are young so the desires to is still there.
I won't date a woman younger than 22 and even then I am not sure if 22 is too young or not. The only reason I say that is because I know a really beautiful, mature and sensible woman who I'd ask out if she didn't have a boyfriend.
Because you are beautyful, cute little creatures. And because milfs and coguars eventually pretend "too much" expecially when they reached pornstar skills, therefore it's quite an effort to make them happy :)