I see landlords like ticket scalpers -- they have the money up front to buy a product, and provide 'liquidity' and 'free markets' by selling that product at the market rate.
For some reason, we generally view ticket scalpers as negative, and landlords as "just what you do when you get wealthy enough".
And, to be clear, I have been a landlord. I know the challenges in maintaining a unit, finding tenants, chasing down rent, dealing with legal challenges, wondering if I would need to evict someone because they were destructive/loud/etc.
(Ultimately, I paid back all the rent I had collected that contributed to my principals on the unit, keeping only the money I used to pay for maintenance. My feelings about landlords come partially from being a landlord and realizing that I was profiting off of people only because I was rich enough to afford a house in the first place.)