[hn_throwaway_99]

Because many of these billionaires come from countries where their political systems are rife with corruption or otherwise unstable, and oftentimes they received their wealth through dubious means. This has been well documented for many residences on Billionaires Row in Manhattan, so much that laws have been passed preventing hiding identities through shell corps.

Buying real assets is seen as a way to protect their wealth when it is at risk of being confiscated or devalued by their home governments.

Another way to think about these apartments is similar to art. Billionaires spend obscene money on art, and they aren't renting out those paintings or really even looking at them very much.