Dating is different than marriage. Sadly women in their 20s won’t share many firsts with you either. The best you can hope for is someone who actually value sex and relationships - aka not a cock carrousel rider.
I don’t think it’s the majority. I think it’s a way higher number than our parents experienced, and it’s a number that’s way too high. But most people probably sleep with who they consider their partners. Sure there’s one night stands and such and tinder has increased those “hookup” numbers, but I don’t think most women are whores.