The whole point of charging for the parking spot would be so that they wouldn't have to use tax money to maintain it.

It's not a matter of alleviating your tax burden, it's a matter of alleviating everyone else's tax burden so they're not subsidizing your car. You should pay for what you use unless there's a compelling reason for it to be subsidized, not the other way around. Roads are essential for freedom of movement and in any case are too difficult to toll on a massive scale, so it makes sense to subsidize them. Parking spaces are inessential and easy to charge for, so we should charge for them.

Nobody is subsidizing your car: as a car owner, you already paid 1) sales tax; 2) yearly registration; 3) yearly property tax; 4) taxes included in gas. Why car owners should be double-triple taxed?

Those costs are minor and not close to covering the cost of car ownership. https://www.theatlantic.com/business/archive/2015/10/driving...

Those don't come close to covering it all. Especially since I don't pay any (4).

Paying to store your car is not a "tax" so it cannot result in being double-taxed. It's a standard payment in exchange for use of property.