That's mainly because don't actually own the land even if it's paid off. Based on our current ownership system you own indefinite interest in the land but the county, state, or federal gov actually owns it.

Our current system is called "fee simple" ownership which is, effectively, the highest level of ownership (aside from the crown) back from the feudal era. Under this system you own equitable interest in the land, it cannot be taken from you without "just" compensation. However you're subject to taxes, rules, and regulations by the ACTUAL owner which, is not you.

The only way to own land outright is through allodial title. THAT is the highest form of ownership because the contract is essentially between you and God. No one can take it, no can tell you what to do with it, and no one can tax it.

Alternatively, in a recent discussion another anon suggested a constitutional amendment guaranteeing us the right to own property which would fix neither all of the ownership issues in the country.