Bear with me I don't know much about bikes but I have this honest question: why does it need a chain, and won't place the engine (or whatever gear box it has) directly on the wheel?
replies(8):
E-bikes can have the motors on the wheel (hub-drive) or on the pedal (mid-drive). This choice is largely related to how much you want your e-bike to really be a scooter or really be providing pedal assist. As a consequence hub-drive e-bikes typically have a throttle while mid-drive do not.
A good mid-drive e-bike really makes it feel like you are a super human cyclist rather than riding a scooter. It leads to a much smoother riding experience if your aim is to still be essentially bicycling but you'd like to get moving faster and not break a sweet even on the most extreme hills.