Because if no one was paying rent, (eg: under a theoretical system of universal basic shelter) what would be the benefit of hoarding more than what you could use?

It’s valuable and precious the same way air and oxygen are valuable and precious, and while we charge a little bit for water, we don’t charge >50% of someone’s income for them to have access to water, then remove their water if we arbitrarily decide they’re not drinking it properly, and make them submit a 7 page document and provide 4 references to get a cup.