I worked homeless services for 10 years. Most homeless people are “normal” and get help and get off the street. The chronically homeless are like the people you described.

My feeling is that for both the substance users and the mentally ill the only thing that really works is being ready to help them when they finally are ready. Sometimes that happens in jail or the hospital. Sometimes they get fed up and want to try to change. Either way, forcing them to change doesn’t really work.