Three reasons. It's a store of value asset, a speculative asset, and a real option that the law will get changed.
Also, these kind of things get priced in, leading to lower property values. There will always be a willing buyer as long as the market price is above $0, implying that the benefits exceed the costs of ownership.
Rent controlled buildings are priced in during the sale so they go for lower values. As for why the very original people even bothered to invest in the building in the first place, then the answer is that the regulatory environment was one that allowed of incentivized it back then.