Assuming for a moment that the fees were of a reasonable amount I see two huge problems with user fees.
1. It would increase the number of NORDOs out there. I realize you can fly safely without a radio but the safety consequences of a bunch of people flying around without talking to each other should be obvious.
2. Collection- how would it be done? Surely not just by radio, anyone could just use anyone else's tail number, ATC could copy it down wrong, that seems like a complete mess. Is someone going to come out to the uncontrolled fields and write down tail numbers? What about the controlled fields, is the tower going to take time from their duties of preventing traffic conflicts to read tail numbers through a pair of binoculars and log them? This all seems like a complete mess.
Then what, do I get a bill in the mail at random intervals? Great one more thing I have to keep track of. Will I have to sign up for a subscription? Better but again that seems to be asking for some "tail number sharing".
I don't see a good way to do it.