First, not everyone has close friends and family. Second, dysfunctional families and bad friends are absolutely a thing and can even be the cause of problems.

Friends and family can be an important part of rehabilitation, there's no doubt in that, but I don't see a reason to abandon people just because those have failed them, if they even had them available to rely on at all.

> why would one expect a monolithic system to do any better?

Because such systems have the resources available to hire and manage trained professionals. What in particular do you think makes a monolithic system unsuitable for solving the problem of effective rehabilitation?