I don't know if 2 kids on a scooter represents bad parenting.
In the summer I live in a place that reminds me of the times I grew up. Kids get dirt bikes and quads when they get their first pair of skates, the play hockey on frozen anything -- outdoors at -25. The ride bicycles (omg!) without helmets.
This weekend I was at a friends place, he has an 8 and 12 year old. The 8 year old rides a Honda 70 like he stole it. I was hard pressed to keep up with him on a little Kawi 140 through some pretty crazy single track trails. He was begging his dad to let him drive the golfcart, so I took him. The kid scared the **** out of me on a little trip thru some ATV trails. He knew ever jump, every puddle, and every stupid incline a golf cart could barely manage and ran 1/2 an hour floored. I was pretty sure the golf cart was going to explode, not sure if I'd leave in one piece.
The moral of the story is kids learn a lot about danger by doing. They learn how to avoid it, and where the limits exist. Bubble wrap them and they might be good mathletes, but they'll miss a lot of they never feel a real body check, tackle, or a tumble off a dirt bike.