Well, driving a vehicle on the road is a lot different from bumper cars. Car crashes are a scary thing. x[
And they're good restrictions mostly, to ensure the safety of whoever's driving, but each year I have less of them until I turn 18. Past 18 I can drive like any other adult. Essentially the state wants people to learn to drive in those years leading up, which is what the restrictions are for. Not a bad system, really.