Depends on your local laws. In my city, bicyclists are treated as vehicles and they require no registration. This includes e-bikes (self built or not). So in my case, “road legal” requirements wouldn’t be an issue for me. For people living in a town, city, or state that has little to no provisions for bicycles on a roadway, this would likely be an issue for them.

the only thing this does is make riding bike paths illegal. you don't want to be pedaling an e-bike with no assist.

It is if you just buy an already road-legal gas scooter and convert it.

Most older 2-cycle mopeds/scooters can be found non-running for like $150, and they'll come with the registration, hi/low beams, horn, etc.

From there, you just gotta be sure your conversion isn't getting too wild since most states now have a provision that states a maximum motor wattage for a scooter to still be a scooter (usually around 1200 watts).

The downside is the effort for the conversion - it's def more involved than a bicycle. And you gotta insure, plate, and register it (very cheap, but still...)

The upside is that you get a legit, road legal e-scooter and for some reason a scooter in traffic going 30 mph is just way more respected than a bicycle going the same speed. It sure "looks the part" if nothing else.

I’ve been building my own roads for years.