So occasionally I look out of curiosity and the reason is pretty plain.
I look for houses for sale in a suburban area as public listings, and there's like 1 within a few square miles of the area.
I switch over to renting, and there's like 12 houses just like the one for sale available, all owned by companies. I also know a coule that aren't listed that have no tenants, but are still owned by one of those companies. You can tell because those yards are now waist deep grasses (in an area where HOA throws a hissy fit if your yard looks just a smidge unkempt).
Don't know why the companies find it more profitable to buy houses people aren't looking to actually move into, at least at the rent they are willing to accept. If I fully understood why, it might just piss me off more. Like maybe the houses work better as a loan basis than other assets, so even empty and unused they are valuable as some sort of financial trick.