"letting property sit idle benefits the landowner"

Can you help me understand this? I've never understood why any property sits idle -- the property would need to increase in value fast enough to counteract property taxes, just for the owner to break even. And that's ignoring the opportunity cost of not filling the property with tenants.

To me, it seems that it would always make more financial sense to try and hit 100% occupancy, even if that means steeply discounting the rent. Wouldn't an empty property be hemorrhaging cash?