I feel it can be unsafe for people to ride electric skateboards and scooters on the sidewalk when people are ride them at a fast speed around people who walk slower. There is a chance people don't see a skateboarder or scooter rider coming down the street, and the people on the sidewalk get roll over by a skateboard and scooter.
Well, electric scooters are bad for the side walk.
But electric skateboards.....I don't know....you can't exactly ask those people to use the road either.....