Rent? variable? It's one of the most predictable expenditures.

I'm not sure if that's more or less cut and dried than "hey I don't have this money anymore because I had to pay money to not be literally homeless".

Deductions are an approach to reducing tax burden, but ultimately we have to decide if more taxes or less taxes are the way to operate our societies. The federalized tax system allows different states to experiment with different approaches, and these kinds of deductions incentivize behavior in one direction.