I agree partly, but there is a ton of subtlety about signalling a move out into traffic should leave a hand for the rear brake. Here is a good answer to that issue from Quora.

I can't speak to scooters if you mean the modern uprated kids toy device, but for mopeds which were also called motor scooters in the UK the brake layout seems to have settled down internationally to I think rear on left, front on right. But since almost all of these today have turn signals that can be operated by the thumb there is no need to hand signals, see above.