if you're not on a parking spot, then yes it bothers people, and you can get fines for it.
* Two-lane road with no shoulder? Fine to park.
* Pull it up on the sidewalk? Fine to park.
It's a pro-car, it's-okay-unless-the-curb-is-yellow shitshow.
The previous poster was being slightly flip, but even in the US, there are places where you can put your car almost anywhere.
But to answer: Because people pay taxes for their vehicles, so the government uses a portion of that to pave roads, and provide some parking spaces. Also some parking spaces are paid for by the hour.
So if you are willing to pay scooter taxes, then Im sure that they would also provide scooter spots.