Nothin' personal, just usin' your post to make a few points.
"I'd go on the ride."... Probably 80% or better chance that there'll be no problem, but who wants to be around when the parents decision bites someone on the ass?
"Sounds callous, but it's not my kid." ... Only sounds callous to the politically correct whiners, but again, do you or I need to be tangled up in the parents problem?
"Natural selection" ... Couldn't agree more, but it still leaves *everyone* on the ride in a discussion with the cops if something goes wrong.
Lots of us rode younger than the kid in question. For most of us it wasn't illegal back then. The highways were different too. More courteous drivers, less congestion, etc. Times & laws change, not always for the better. I too would like to see less of a "Nanny State", & I sure as hell won't contribute to it by callin' some "authority" about the parents, it's their kid & their lives. But, I think it's in a persons own self interest to avoid obvious problems. It's one of the things the "strong & smart" do to survive.
OTOH, if the kid had a license & insurance I'd be one of the first to give him a chance! Along with being one of the first to get on his ass if he screwed up, & the *very* first to ride away if he didn't straighten up.