Hams self-police because our spectrum allocation is a privilege from the government that can be taken away if people don't play by the rules.
Also, a valid address for your license can be a PO Box if you care about your personal details being online.
Doesn’t help that the HAM community will more than happily snitch on you if you goof around too much, and licences mean your full dox are publicly searchable (at least in America).