@nuncio because adults acted in gross neglect - that's why.

The problem are adults.

Needless to say there are some "not legally cars" that under-18 can legally drive and own depending on their juristiction, but those are either "cabin tricycles" or "cabin scooters" or similar constructions limited in power and speed.

Like the [patented] #Ellenator conversions...
https://de.wikipedia.org/wiki/Ellenator