They make me nervous, bc, as other commenters have pointed out- brakes, suspension, and traction matter a lot.

The difference between the cheap version of a motorcycle and the sport version isn't the engine, it's the brakes and suspension ( and now electronics).

But the main thing is the lack of helmets. One motorcycles, the center of gravity is low. You are more likely to fall and slide than go head over handlebars. At motorcycle speed, you should be wearing a full face helmet. I very rarely see the guys on e-bikes wearing full face helmets.

Then you look at the wheels and tires, higher speeds means more acceleration and faster stops, means more wear- which means much more maintenance. That most people aren't really paying attention to. Maintenance on two wheels is more than just a reliability issue, it's a safety issue.

Finally, people give no respect to bikes on the road. Especially in the US. You could be cruising along at 30 mph at the speed limit and someone will feel the need to pass you because you're on a bicycle.

As in I would rather ride a motorcycle on the road than a bike. On bike trails, a regular bicycle is great. Where there are very few cars or very good bike lanes, electric assist bicycles make sense to me. But when you have bicycles going at car speeds mixed with cars, but without good brakes, without turn signals, etc. I would be very nervous to get on one. They aren’t built for that speed and roads aren’t designed to handle them. Moreover, most drivers don’t expect them. I can be on a 900 lb motorcycle and still be invisible to some drivers. Now imagine what I look like on a tiny bicycle that’s zooming at 3x the speed most expect from it.

Here in North America, most ebikers just wear bicycle helmets. Bicycle helmets are only rated for a fall from 2.0m onto the ground, or about 22km/h. [0] Ebikes tend to go much quicker than this.

[0]https://www.astm.org/Standards/F1447.htm