Because people actually live in those. And, because of the never ending housing crisis, the "value" of houses goes up pretty rapidly. Which already sucks when you are paying property tax and needing to send the "Hey, my house isn't ACTUALLY worth that much" letter to the county every few years. But add on an overall tax for... not paying rent? And you are going to have a LOT of people priced out of owning their own homes. Which, like most of the previous poster's suggestions, just serve to consolidate "wealth" with the ultra-rich.

Multiple homes? Fuck 'em. Yes, there is the occasional case of someone buying their parents' home or whatever. But mostly you are looking at landlords in that situation.