And who will be the most affected? “The poor and the children”. It is all about revenue.
I still haven’t figured out why school buses do not require seatbelts and, now, booster seats. But, individual vehicles do.
The law would be unenforceable. The bus driver would have to stop the bus and continuously walk back and forth between seats checking the seat belts. Even then some children would unbuckle as soon as the driver is not looking. He can't punish them for that, can he?
If then the bus is in an accident and some children are not secured in their seats, who is going to be responsible? The driver? But he can't see his passengers. Children? They can't be held responsible for their actions. Thus the law would be an empty word, free to violate with no repercussions.
One can argue that the driver of a car also can't be constantly aware of the state of seat belt latches at all times. However we don't let strangers ride in our cars; any miscommunication or intentional violation will be then between the driver and the passenger - and, unlike in the bus, next time that passenger will not be allowed into the vehicle.