I'm on the fence with this one. My opinion, it comes down to the individuals involved. The first drivers didn't have licenses or training; the first pilots "winged" it. As a volunteer and professional firefighter with many certifications (structural, wildland, medical, technical, etc.) I can tell you that when the crap hits the fan, a lot of how someone responds depends on who they are. I've seen highly trained individuals freeze up at the moment truth, and trainees adapt to the situation like an old pro. Sure, training is a great thing, but for an "intro" scuba swim, it doesn't seem like the sky is falling to me.
My daughter (18 y.o) wants to try scuba. I handed her the NOAA dive manual and told her to read the first few chapters, because there WILL be a test. When I'm satisfied with her understanding of the risk, I'm sure we'll head off to the pool to give it a try. If she wants to pursue diving, I'll arrange proper instruction with a friend. Hell, I took her skydiving for her 13th birthday, which was kinda funny, because it gave her the distinction of taking off in an airplane, but never landing in one!?
So I say let's not take ourselves so seriously. Sure, there are risk, but it's not like we're walking a tightrope across the grand canyon.
J