What I don't understand is, why aren't secondary dwellings taxed extremely heavily? Optimally, nobody should ever have to rent their residence for a prolonged a

What I don't understand is, why aren't secondary dwellings taxed extremely heavily? Optimally, nobody should ever have to rent their residence for a prolonged amount of time, which means you need to disincentivize sitting on a property you don't live in. Making it hard to profit over time from such an investment is the only solution I see.