Ah, on that way. Well first of all, I am a coder, and I did code websites in the past. In other words, I know what a dangerous and tempting place the internet can be. However since I'm in my forties I know that loads of things are too good to be true. When it comes to underaged users I can fully understand that websites cannot bear the responsibility for any negative effect the presence of children can cause, and yet since children can by law not be held responsible for some things....
When I was a teen, we didn't have internet, or at least not on this scale we have it today, but we did have age restrictions on stuff like games and movies etc, and back then I felt it was bullshit. Now I think that even some adults should be taken away from certain things, let alone children. Now, age is just a number. Each kid grows up in their own speed. Some kids can take loads of responsibility and take a lot when they are 14, others at 16 and some don't really get mature until 25... In other words, just a number of years cannot determine what is suitable for you and what is not, however they need to draw a line somewhere, as sorting this out for each kid separately is undoable, so taking an average age line was the way to go. It's far from perfect, and it's certainly not a measure taking the win in a beauty contest, but it's the least bad solution we got, I'm afraid. It's not I'm happy with it... In Dutch we call this "noodzakelijk kwaad" (lit. necessary evil, or needed evil... It means that people hate it for good reasons, but that it's all we got so it needs to be done).
I've met 13 years old kids act more mature than some 40 years old, so that's why I mixed feelings.