If riding a bike was as common as a car it'd be regulated all the same.
You already see "certain demographics" that suspiciously always seem to feature prominently in any given decade's policy failings screeching about how e-bikes need registration because they let people they don't like have easy geographic mobility.
Regulation of cars , like anything, is expensive. It’s worthwhile for cars for safety reasons, but bikes are cheaper, and also way less dangerous in general, so need a lighter hand.
The current cutoff in EU is probably right, above a certain power level, e bikes are l, broadly, treated an motorcycles (licensing, type approval, insurance etc) , below that and with non-e bikes, is really just about the basics, eg are the wheels firmly attached and do the brakes and lights work?
You already see "certain demographics" that suspiciously always seem to feature prominently in any given decade's policy failings screeching about how e-bikes need registration because they let people they don't like have easy geographic mobility.