A guy wants a nice girl for a girlfriend, someone they're serious about. But a lot of young guys don't want a girlfriend that they're serious about. They want easy, regular sex. They know 'nice' girls come in a package and won't just sleep with them, they want a relationship - whereas they know they can get the skanks into bed without having to do much or make a commitment to them or even care about them. Nice girls are too much effort.