15mph and has a throttle = electric motorbike (and also illegal)...
But make that 15mph illegal electric motorbike 10mph faster and add extra hardware so users have to waggle their feet around in a circle to trigger the motors... SUDDENLY LEGAL!
I highly doubt there are any safety benefits from pedalling - it seems like an arbitrary limit.
Of course it is, all limits are arbitrary, even if informed. Lawmakers probably picked limits which would be reasonably achievable by average healthy humans over long distances.
I should have really said purposeless!
Usually limits have a purpose - for instance limiting the speed of cars by law is because of accident reduction.
Unless the argument is that pedalling makes it safer, it seems to be a limit for no particular reason.
The point of pedelec regulations (in europe anyway) is to be a baseline: anything which satisfies the pedelec specs must be treated as a bicycle by all member states, so if you have a pedelec you know that it will be usable as a bike throughput the union. Member states can go beyond if they want to.