Yep, it's down to whether people enforce it really.
We've got basically the same rating system across forms of entertainment but there just wasn't an Adult rating when it comes to games.
So in a case where you'd have an adult rated game in places like America - it would either be banned / refused classification or bumped down into the 15+ category - meaning teens have access. Not really ideal either.
Honestly, A lot of stuff that has been banned is just trash anyway but it's nice to not have that restriction.