(Feel free to replace man with woman, etc. I'm too lazy to do it myself. Sorry. Oh yeah, and in speaking of coming of age activities/rituals, I'm not speaking strictly of small tribes in the rainforest. We more "developed" peoples have our own...)
Ah, the flexibility of our culture.
Used to be that you'd go out and perform , and then you'd be a Man. Nowadays, there is no ritual to perform that makes you a man. You just... are.
In some ways, this is a fine thing. After all, piercing your cheeks with sharp twigs is distinctly unsanitary, and a bit, well, brutal. Although I can see how, in some ways, it can hasten adulthood... By requiring each person to individually reach adulthood, our adults are probably stronger. After all, it's one thing to have someone say "You are an adult now", while it is another to claw your way up to the point where you can claim it yourself, and none will argue.
In other ways, it's a bad thing. It's easy to stay a child - as I'm sure some so-called "adults" you know have done. Indeed, I think that one reason so many coming of age activities are painful/violent/gorey is to act as a slap in the face, a sort of shock therapy, saying, "Guess what! You're a Man now. That means that you need to be able to handle yourself, whether it feels good or not."
Not that it always works. But I think in some cases, the coming of age, and the preparation for it, do help.