I don't believe in "13+ sites" that are restricted. I think a person should be given this kind of access in their late-teens or early adulthood. Primarily for these three things;
1) They often still aren't very mature enough to visit the website. I mean, come on, they're thirteen.
2) By restricting some things, these websites can censor things that would normally be fine to thirteen-year-olds
3) By heavily limiting access to the internet, a child can find the time to do other things that may be more helpful.
