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 as

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.