a lot of parents don't even know what the Ms and 18s on the box mean. I'm still traumatized from talking to a parent once who thought the age rating was referring to DIFFICULTY like it does on board games or puzzles....
I remember when I bought Metal Gear Solid 3 back in 2004, my mom had to be there with you to get her permission.
Granted MGS usually only had mild cursing so I dunno.