I think the biggest advantage scooters have over ebikes is that for a lot of people, there’s a place to store a scooter at both ends of a commute (under a desk) but not necessarily secure bike storage.
Bicycles in big cities are too inflexible. If all you want is to commute like a sheep from home to work and back to home every day then a bicyle is a great inexpensive and green choice, in every other case it's a problem. Unless of course you are in a small village, where a possible change of plans will still result in a short ride. In London this is not possible. If I was to meet friends spontaneously outside my daily commute area then it would be impossible with a bicycle.
The smallest folding bicycles (e.g. Brompton) are fine, but scooters must either be balanced upright, exposing dirty wheels, or take up a lot of floor space. No thanks!
In the largest cities like London, if my plans changed I'd just leave the bicycle at work, and take public transport to the party, home, and to work the next day (unless my way home passes work, then I can collect the bicycle).
It doesn't matter how slow you pedal, in the American Southeast, just being outside in the summer makes you sweat. A lot of places in this area don't have offices with showers in them. A scooter let me spend time outside without having to end up being a mess.