It's not exactly the problem that the government is acting as a surrogate parent. It's that they're taking this too far because the parents are shirking their responsibilites themselves (and I don't mean in a passive manner, they screw up in a very active way)
Sometimes a kid can get their hands on a game because a store is dumb enough to sell a violent game to them anyway, but this actually doesn't happen often at all, especially since stores, due to all the controversy, have been enforcing the rating system more and more themselves.
Most of the times, however, it's not because of the store. Most of the times, these kids will get their hands on these games because their PARENTS know nothing about these games, apparently taking ZERO interest in their child's hobby, and will actually BUY them FOR their kids. Subsequently they will nag at the government because it was possible their pure, innocent children got exposed to this kind of content despite their perfect parenting.
So, who is making the biggest mistake here? The parents.