The scarcity isn’t primarily the beds.

Obviously not. The existence of homelessness isn't due to scarcity at all, it's to do with a system that tolerates (even necessitates) homelessness. The image could have just as easily been someone sleeping outside an apartment with a sign advertising available units; they sleep, freeze, and starve, because our economic model rejects their basic needs in favor of commodifying them.

It's not that hard a concept to grasp, it just seems like people have ingrained the logic of the market in their brains and can't conceptualize the issue of poverty beyond 'stuff costs money'.