When I was 17 years old, I was riding my BMX bike down a road at my normal "cruising" speed. At some point, a guy in a Jeep paced me. I was weirded out and thought he was going to hit on me as we pulled up to a light. Instead, he looked over at me and asked me if I knew how fast I was going. I said no, I don't really care. He said I was maintaining a speed of 30 mph and was quite impressed. I was not impressed. I was not trying to be fast, I just get bored taking too long to get anywhere and my bike was my only form of transportation until I was 27 years old.
Limiting e-bike speeds to under 20 MPH seem utterly absurd unless there is bike infrastructure leading to EVERYWHERE. Cars are utterly dangerous to people who are slow. A bike needs to be able to keep up with traffic for short periods, as road usage is inevitable with the utterly shitty bike infrastructure that is available.
Maybe have a few police officers hang out at certain locations from time to time to discourage the people who use speed stupidly; but making bikes slower than a dude pedaling a BMX bike with his own legs is just stupid.