That's true, although jail isn't going to help either. My SO did corrections nursing for a while, both at the county jail and state prison levels. It was possible to administer rehab at the state prison, but it was impossible to do it at the county jail level.

They're in there just long enough to start detoxing before they're released, either with a token bail ($100) or just straight-up on their own recognizance. Then they go get high. Sometimes they overdose right then and there. In any case, they then miss their court date, (no shit) get a bench warrant, and then get arrested once they overdose again or piss on a telephone pole or whatever.

Wash, rinse, repeat. Sometimes they go in for a few months once the judge finally gets annoyed and sentences them, but it never helps; they go right back to getting high as soon as they're out of jail. It doesn't help that they're nonviolent and the jails are overcrowded; they're likely to get released early to make room for the gangbangers. Predictably, this makes it even more likely that they're going to walk out the door and immediately look for a fix.