In the U.S, to get into an R-rated movie without a parent you need to show ID to prove that you are 17.

But you can watch videos of people being beheaded in subreddits by simply signing in.

My point is that if a society decides that certain content should be age restricted -- it being on the internet shouldn't make the difference.

I largely think that age restriction laws are ridiculous. BUT, I don't think the internet is some special haven, exempt from all of society's standards/laws enforced offline.