Why is it so popular to whore yourself out?

This isn’t at anyone specific, but I’m just genuinely curious why it’s become the norm to pride yourself on being a slut? Like I get the idea of open relationships and I have nothing against those.. It’s when one party is completely unaware of this that I draw the line.. Since when did cheating on people become the new popular thing to do?

I’m not like other girls, my mom says I’m not as emotionally or mentally prepared as most teens my age