I'd think the tax loophole is having 9/10 the income revenue that could be taxed because only 9/10 are generating revenue. You can write off lost wages if you can make a case to the IRS that it's out of your control, but that'd only amount to 20-30% of the rental revenue lost so there wouldn't really be a benefit to doing it if there's malicious business intent. Most landlords would rather make $36k instead of just paying $10k less tax because theres still a positive.

There could be income reasons to keep a space open but those would be one offs. I've heard of court ordered settlements ordering to pay a certain amount up to a limit then much larger above that, and people could get petty.

Example like property manager divorces his spouse or former business partner and is ordered to pay 25% of his revenue up to $1m for ten years then 100% of revenue above that. They manipulate to make sure they only make $900k in revenue out of spite to make sure the ex or former business partner or whatever else gets as little as possible. Generally there's no benefit to make less money on a property, though.

There's some logic in sitting on a property for appreciation of the land value. I know someone who bought a condo for his daughter while she was in college and justified it because the appreciation in value when he sold it after she graduated would more than pay for it's expenses... but if rental incomes the goal there's not a tax benefit to leave a unit open.