Most Helpful Girl
Well, sometimes they're actually not interested and guys think they're playing hard to get when they actually are hard to get.
Other times, it's society's fault. There is a lot of negative social stigma for a woman who pursues or who agrees too willingly, so they play hard to get to maintain their dignity, so to speak,
There's also the possibility that women play hard to get to see if the guy thinks they are worth the chase. If the guy gives up and moves on, the woman knows he was not worthwhile.
But of course it depends on the situation.