Also because they get moldy and stink from the humidity, and because many people believe they have ghosts.
The absolute quickest way to kill home value in Japan is have someone die in it. Absolutely nobody will want to live in the place and property owners will warn you before you consider looking at it.
If old people in the US saw their homes as a time-limited investment where they needed to sell them while they still can in order to ensure their spouse/kids have money, prices might drop. Maybe bringing back superstitions is a way millennials can finally take back the housing market.
So I guess the most realistic path would be for the big one to hit California and destroy all the housing stock.