[mikro2nd]

I think that at least some of this comes about because it's still relatively early days for the form-factor. As the industry matures, as it becomes more cutthroat everything will become more comodified and therefore standardised.

Look at some of the cars of (say) the late-19thC where not even the steering wheel was standard. So, while e-bikes are probably not quite that early stage right now, they've not advanced terribly far from the plain vanilla bicycle yet.