That's more of a testament of how fucked up housing is in your area. That would be like saying tents are more vital than housing because many homeless use them instead.

Car rentals aren't as much of an issue, because of how much less expensive it is to own a second-hand car. If you're homeless and you need access to a car, you don't go to a rental place, you get a beater from Craigslist for about the same price it would cost to rent a car for a month (if not less).