So no hope for treatment? Since you say you can't rely on them to stay on their meds and locking them up for the rest of their lives is the only option? Hey congrats our panel of experts have diagnosed you with a mental illness so you will be in protective (to the public) custody for ever. Sounds like the UK's method of handling those with mental illness.
A select few will comply with treatment, and that is a great thing. The vast majority of the seriously mentally ill are noncompliant with treatment, from taking their meds to showing up for routine apppointments with their therapist. They do this for literally decades, in and out of jails and mental hospitals the whole time. This causes a tremendous amount of suffering, both for the sick person, their friends and family, and society at large. Often the family reaches burnout and cuts off contact with the sufferer. When your MOTHER cuts you off, you're in big trouble.
This is me: other people's rights stop where mine begin. If you as a paranoid schizophrenic have choked your grandmother to death with your bare hands some months ago (one of about 50 instances of seriously criminal patient behaviors I can think of, from personal experience), REFUSE to comply with your psych meds, you get out of jail, burn down two houses, threaten your girlfriend and her mother with a loaded shotgun, and then carjack three cars in one weekend, guess what? You need to be somewhere so that society can be safe from you.
The sad thing is, if they took their meds we could avoid all this. But most of them won't. Many psych patients are really paranoid about their meds, thinking they are poison or a chemical neutering device or implants from the FBI or any one of hundreds of nutty things. These people need management, not least because the next house they try to burn down may be your own. I have no desire to get thrown off a subway platform in the name of someone else's "freedom"!
I do not lack sympathy for these people, but I see this stuff every day and I have no illusions about most patient's management of their own cases - or lack thereof. God bless the few with the insight needed to take care of themselves, for they are.... pretty few.