Any thoughts on the mechanics behind this? For any wheel size and range, a scooter naively seems like it is going to have strictly less metal than an e-bike, so I would have thought they would be lighter.
The frame of a bicycle is probably a lot lighter, as a sort of triangulated truss - compared to the "solid beam" style of a scooter. Disadvantage is it takes more space.
You don't pedal on an scooter, so the battery needs to be big enough to carry around both you and the larger battery (adding weight). Conversely, e-bikes can assist your pedaling (rather than having to replace it in all cases) so they can be lighter.
A scooter is a flat plate with a steering column adding no strength. A bicycle is two triangle elements of pipes.
I wonder why nobody has done electric rollerblades yet.