People have a lot of training before they can go on a big bike (or they should have if their training school has anything about them), personally I think the age/power restriction is a good thing. I passed my test at 19 having done 3 years on L plates, I'm now 24 and have no points and 1 accident (a driving instructor pulled out on me and i threw the bike) I worked my way up through many bikes to the 5 I have now the largest being an FZR1000. Each bike taught me a lot about riding and respect for each machine I get on. I have taught lots of people to ride (I'm an instructor) and there are some of varying age that I have seen pass their test and thought you are not going to stay in one piece very long, so I dont think it can all go on age and experiance either a lot has to do with a persons temprament and do they respect their bike and know their own limitations.