If they are renting them out, the homes are not being hoarded, they are being lived in.

The real problem isn't a problem of vacant units, it's a problem of unbuilt units.

This results in a transient population and concentration of wealth, and reduced overall housing security. A mortgage doesn't go up by 10% every year, but my rent sure does.

Why do landlords have the power to raise rents 10% per year? Because there's not enough housing being built. Every unbuilt unit leads to displacement and rising prices.

When you say "This results in a transient population," I'm not sure exactly what you mean by "this" but perhaps it's renting at all? If so, the only reason renting leads to "transient" population is the rising rents and displacement caused by lack of building.

There is no lack of building. There's an insane amount of single-family and multi-family construction going on where I live, far in excess of natural population growth. But corporate landlords are buying up entire neighborhoods and replacing for-sale signs with for-rent signs. Corporate landlords will squeeze every penny of rent increase they can out of existing tenants, because moving is hard and they've blocked all the alternatives.

Corporate landlords, or really any landlord for that matter, can't squeeze anybody if they have other options. And in my personal experience, mom and pop landlords are just as greedy as corporate ones, but are less rational and obey the law less frequently.

> There is no lack of building

Putting something in italics doesn't make it true. In the vast majority of high demand areas, there's a smal smattering of new construction, far far less than comes close to meeting population demand, and locals freak out about the construction and vastly overestimate the amount. If your particular location is building 3%-5% more units per year, great, but most of the country is not and that means that every other place that's under building is displacing it's residents to where you live, easily swamping whatever you call "more than natural population growth"