Because the accident, injury and insurance data all supported the case for tiered licensing.
Yes lots of inexperienced riders crash harder and die more frequently because their first bike was too much for them. Go talk to medics in a trauma unit.
I want to agree with you, but can not
Having a proper training and testing that what will change things for better, imho, and it should be done for cars as well. Want a bigger bike spend few weeks in training before trying it, you'll pay more upfront but it would be a good barrier for school kids. Have a proper exam, not just parking lot drills. Do 1-1 sessions with instructor on different roads, so they can evaluate your abilities, and so on. It just simple stupid to get any license now.
Another thing people should understand that any vechile is a "object of higher danger", I want people to treat those as "lethal weapon" before even trying to get a license.