Easy. The same as why you don't tax people for sidewalk use. Car infrastructure is expensive, very expensive. And the need of having specific bike lanes have be

Easy. The same as why you don't tax people for sidewalk use. Car infrastructure is expensive, very expensive. And the need of having specific bike lanes have been imposed by the increment in presence of cars in our roads, not by the bike needs themselves. As for the plates, similar explanation. We don't need a plate on humans, as usually identification can be done ín-situ if required. On top of that, you want to reinforce the use of bikes, and not reduce it. Increasing bureaucracy for bikes will not help at all.