[burntwater]

I always wondered how they benefit from this...

If it's anything like NYC, they (I'm assuming you mean landlords) benefit through tax write-off. They can write off the lost income while they wait for a (hoped for) higher paying tenant.

[fred_is_fred]

Unless you know some pretty odd tax laws one cannot write off the act of refusing to make money. They can write off business expenses which on an empty building are likely to be not too much different from an occupied one (some are more, some are less). I think that in some cases waiting for more rent is right, in other cases it's simply investors (many overseas) using the space to park assets. They want their money out of GBP or Yuan and in US real estate, but they don't really want to be landlords. See also pretty much every condo in Vancouver.

[kgwgk]

I also save a lot on taxes by writing off the lost income from the one-million-dollar bonus I never get!