Don't cars generally park in designated locations, pay large amount of money in taxes, often also in parking fees. Even in SF I think you are more likely to walk into a pile of excrement or scooters in a middle of a sidewalk than into a car...
Also, visit any of the neighborhoods on the western half of San Francisco and you'll discover that it's de facto not allowed to be handicapped or pushing a stroller due to cars owning the sidewalks.
Not sure how taxes could be "market rate" to begin with, but don't those scooters just get dumped anywhere without any payments to the city or something?
Also, just one of many reasons why I don't go to San Francisco if I can help it at all.
The taxes you're referring to, I presumed, are things like DMV fees. Those are used for things like roads (construction, repair, salting, plowing, etc), bridges, highway patrols, etc. They aren't market rate because they don't actually cover their stated purpose, thus are subsidized from other taxes. Additionally, they don't price in externalities like noise, pollution, emergency services due to accidents, death and injury to persons, etc.
The scooters are indeed left on sidewalks. Luckily the 20 pound scooters aren't actually killing or maiming people, spouting out toxins into the air, ripping up the asphalt, blaring "honk" noises at all hours of the day, etc. Not much of a public nuisance all things considered :)
Bridges and stuff sometimes pay for themselves in increased economic activity, as do highways etc. Not sure about SF, but in Chicago, say, on top of the state fee for the license stickers (far more reasonable than California's, of course, but still) there is a city fee for a city sticker that has to be applied to all vehicles registered in the city.
Practically speaking, though, as nice as it would be to get rid of cars, pollution, etc., it's not happening unless you can offer something better to the public, and scooters aren't it. And scooters, at least how I am reading news about them right, aren't exactly paying for any externalities either.