Also, "the system" (insurance companies, the courts, etc) sometimes make it very, very hard to get someone the help they need.
I had a mentally ill colleague that was very difficult to help. His family was ready and willing, but it was just impossible, given the legal constraints on everyone, to get him the help he needed. He was homeless for 6-9 months before he was committed and then got back on his meds and was able to go home.