A long time ago, all bicycles had license plates.
I had a bike with a license plate on it, so it was imposed on kids too.
If I remember right, it was about $3.00 in 1970's dollars.
I don't know what that comes too in todays money.
It was a form of tax I guess.
That has since been removed.
I think a mandatory license plate would help identify those that constantly dis-obey the law.
A quick picture or film would do it (photoshop would really help in this. hehehe).
If well managed, it would also curve the theft of bikes.
You wouldn't be able to register a stolen bike and plate it.
And what are you planning to do with your one and only life?