If I look at the rules here in Sweden I find that EV owners also have to pay a car tax as any other car owners. They do get the first 5 years as free as tax bonus, but after that they pay just as any other car owner. The tax is a base value (~36$ per year) and then an additional value based on the emissions and attributes of the car.

Car ownership is taxed because there is road usage, parking, health care, and other costs associated with car ownership. There are also pollution created by the wheels, oils, cleaning products, and so on. To be honest, 36$ per year seems pretty cheap as a base value considering all the cost to society and should probably be raised when more cars become EV and less money is gotten from gas and car taxes. The alternative is to raise other taxes like income in order to fill the gap in the budget or lower the budget of road maintenance.