Because of policies mandating to stop using drugs, follow a specific religion or give up their possessions and live in bunks without private spaces or storage for personal items.
Mark is intimately aware of those programs and the hurdles they can create, he works directly with many of them. However he has repeatedly had people who come to him begging for help, and then they do nothing to actually realize that help. Even the most basic "Be outside your motel room I bought you at 11am to get in the car I will send that will take you to the counselor I'll pay for" and then they ghost it.
At the end of the day, they would in fact rather live on the street doing dope rather than live in a (paid for) motel room (or even apartment) and work a job.
