I do have a motorcycle as well, since you asked.
Why an ebike?
Some sources claim it is actually the most environmentally friendly method of transportation, even when taking manufacturing into account. Over its lifetime, it creates less pollution than bike riding or walking, if you assume the person isn't a vegetarian.
Cost per day to commute 8 miles each way on the ebike is roughly $0.50 and roughly $5.00 for my 25 year old Toyota Tacoma, considering all costs.
I also enjoy riding my ebike and it has some health benefits. I don't just sit on it like a lazy bum who is riding a slow motorcycle. I pedal with moderate effort and can get to and from work feeling like I got some exercise without arriving all sweaty and gross. Riding this distance on an unpowered bike before and after work would fucking suck.
Is the lower speed a disadvantage? Yes but only slightly. I could get to work in about 15 minutes driving vs consistently about 22 minutes on the bike. Although the top speed is only about 28 mph, im nearly always going top speed. There are a few places where I have to stop for lights but at these intersections, I generally catch up with the cars that passed me earlier. Unless you're getting on the freeway, the bike is only barely slower.
It will probably take some time for regulations to catch up but many places already have rules for ebikes. For example, in California, class 1 and 2 are only allowed to go 20 mph (32 km/h). Class 3 can only go 28 mph (45 km/h) and only via pedal assist, rider must wear helmet and be at least 16 years old, aren't allowed on bike paths.
What are the reasons for your distaste?
Hardly anybody wants to ride an analog bike. Yes, it's because we're lazy. People would much rather ride around in their comfortable cars, with their stereo, radio, heater/ac. However, ebikes make bicycling an efficient, viable option that doesn't suck.
Even if ebikes replace some non-ebikes, ebikes are more efficient. There is a slightly greater environmental impact from producing the food to supply the calories to pedal the analog bike than there is from producing the electrical power to charge the ebike.
I you compare the impact of an ebike to an ice or an electric car, it isn't even close. The ebike is far superior.