[mseebach]

I've had two bikes stolen, both correctly registered in every relevant registry and one with microdots. Not a word.

The economics are extremely simple: There is a significant market for "don't ask, don't tell [if they're stolen]" bicycles. The same probably exists for cars which is why it took immobilizers (not frame/engine serial numbers) to curb theft.

A further complication makes a bicycle immobilizer impractical: It is trivial and not even very conspicuous to carry a bicycle quite far, or stick it in a car. That allows you to remove the bicycle to a private location where you can remove or destroy the immobilizer - if you could do the same with a car, I'm sure immobilizers would be less effective.