[reallydontask]

>It's strictly better to rent an apartment out because otherwise you're getting nothing from paying management and taxes.

Renters can choose not to pay rent, can cause untold damage to the property and can use it for illegal purposes to name but a few reasons why it might be rational not to rent a property out, specially if it's an appreciating asset.

I suspect that the majority of these empty properties are owned by wealthy people from countries like China or Russia.