Also, if you're a marginal renter, e.g. can't make 3x the rent from a W2 and don't have a co-signer, credit issues, etc. then the randos are more likely to work with you.

My sister was a sex worker for a while when she was younger, and trying to do things like rent was difficult because her income fluctuated a lot (always enough to cover rent, but she'd save during good months for poor ones) and she was technically self-employed. Or if you're on any form of disability, or if you had a medical issue that trashed your credit, etc. People getting out of prison, and so on.

If you stray from the happy path, woe unto you when dealing with large companies.

Helped my daughter find housing recently and we ran into lots of these issues (also, nobody we talked to was willing to allow a co-signer).

We ended up finding a friend-of-a-friend who had a bedroom to rent, but she will not (at least in the near-term) be able to rent an apartment.