E-bikes are neither commute vehicles (not confortable to sit on) nor sport equipments (whose utility is to improve public health). They're just hobbyist tech thingies that contribute to e-waste. Why subsidise them?
Electric motorbike is another story, but I don't think they're that common in the developed world.
As someone who has an e-bike that's pedal assist, I have commuted 20 miles on a regular basis to work _because_ I'm able to with my e-bike. They enable you to get exercise and travel to a location much more easily over a regular bike. What is the main advantage of an e-bike over a regular bike for me? I'm able to climb tough hills that I wouldn't be able to otherwise.
I commute on a conventional bike, but e-bikes have definitely expanded the acceptable distance for riding a bike to work, for a lot of people. Several of my work colleagues have gotten e-bikes for this purpose.
Electric motorbike is another story, but I don't think they're that common in the developed world.