Yes it does depend on city ordinances just like normal bicycles. Here if there is a bicycle lane the state law requires bikes to use it (normal bikes is what I'm talking about) otherwise it's up to the city to decide what they want.
But just like ordinances exist they can change. To refer back to the 10yr old here (it happened in October) that was killed a nearby city changed their ordinance to have e-bikes and e-scooters to
only be allowed on the sidewalks. They were already in the process of reviewing their ordinance due to increasing public safety complaints.
The new ordinance states for that city
- It being unlawful for any person to operate a motorized skateboard, scooter or unicycle on any street, road or highway system. They are allowed to cross them while using the devices.
- Every motorized skateboard, scooter, or unicycle crossing a road, street or highway, regardless if it’s marked or not, shall yield the right-of-way to all vehicles and pedestrians.
- No person under the age of 18 shall operate or ride a motorized skateboard, scooter or unicycle without wearing a helmet.
The motor aspect is of high contention here in my area for why people want those using them to have driver's licenses as the speed they can get up to. Mopeds require driver's licenses in most states but places haven't quite caught up on the legislation with respects to e-scooters and e-bikes. Cities around me are increasingly paying more specified attention to e-bikes and e-scooter usage especially by minors though.
To be clear most concerns with respects to safety are aimed at minors and yes I agree with your last statement. The sidewalk doesn't absolve risk it just allows for less vehicle to e-bike/scooter incident rate. It still relies on everyone being aware, for everyone to adhere to rules such that they are written. Police enforcement is like other ordinances hard to do until something happens unfortunately. The true answer is agreed that they not be allowed period but in practicality the sidewalk presents the lower overall risk. Here at least. Other areas may have different risks but 100% here if they are going to be out and about not being allowed on the actual street for children is the safer of the two.