On the flip side, there is a finite supply of housing. A retired senior citizen living in a house prevents a young professional from living in that house. Given that the former is going to provide far less benefit to society than the latter, there is an opportunity cost that needs to be accounted for somehow. A property tax is not a bad way to account for the opportunity cost.

> Seniors and retirees are such low impact on society.

IIRC, medical care accounts for more government spending than all other discretionary spending combined. And most of medical care is going to be caring for seniors.