That would be nice, but is often prevented by regulations. Essentially, the idea is that you might always get a car in the future (or move out and sell your home to a car owner), so the parking spot needs to be preserved for this possibility.

Now, depending on how strictly the rules are interpreted, this can mean that you need to provide an actual parking spot at all times even if you don’t own a car (and do not have to let anyone use it!), or you might be allowed use the parking spot for other purposes, provided your changes are easily reversible. (So planting trees or building a shed is off limits, but placing down potted plants and some seating might be fine – as judged by someone of your local authorities.) Having an actual garage might also be preferable as a non-car owner, as that can at least serve as dry storage space while still counting as a parking spot.

Last, the idea is still a bit inane. Japanese-style rules where you need to show that you have a parking spot when buying a car (instead of tying it all homes) would be much preferable in my book. But this is difficult, as there are still many places where streets are so old that cars did not yet exist when they were designed. (And the houses actually touch each other and the street, so there is no place where they could add parking.) These houses are usually exempt from needing to provide parking for their units. Doing it on a house-by-house basis instead of a car-owner-by-car-owner basis is just easier because of this.