Most land is leased rather than owned - which means it depreciates over time. Imo it's a sensible system 70-100 year old buildings often have issues like Aluminum wiring, lead pipes, or asbestos, and can be in generally such a sorry state that renovating them costs more.

Also building a house or apt building that can stand for 100 years is very different from one that stands forever, for example steel beams can be used as foundation instead of having to pour concrete