It's not until the late 20's that the brain is able to make a rational choice when it comes to excitement vs. self preservation.

I can tell you definitively it was 26 when life hit me and I woke up to the possibility of one of my stunts killing me. I notice it alot more when I'm hanging out with my younger brothers.
And your right on with those magazines pushing the riding stupid and fast on too kids. Couple that with dealers who are all too willing to sell that fast rocket to a learner instead of offering a beginner bike. Heck very few companies are making a decent beginner bike now anyway. Starter bikes start at 500ccs now. I can't tell you how many huge insurance policies I have written on the 18 yr kid on the new 600 zoomsplat only to file an accident or theft claim later that year. And most of those "theft" claims are when a kid is goofing off and blows the motor or crashes trying to stunt. Another problem is how cheap a sport bike is? 1/2 the price of a cruiser with twice the power.