Could someone explain why a groupie or a Badge Bunny could give sex for free?

could someone explain why a groupie or a Badge Bunny could give sex for free? groupies are ladies that give rock-star or celebrity sex for free while badge bunny are ladies that have a thing for uniform men and in so chase after them and have sex with them. as a man I know our motive for chasing women is for sex but for the groupies and badge bunny, wont they feel use? I mean, a slut might do it for the money but a groupies why, what is the psychology behind it?