I agree, it's a really difficult problem and there are no real solutions yet... Especially with the diversity of illnesses out there, there will never be a one-size-fits-all solution. But I do think that, because it's so overwhelming, we've chosen to totally ignore it and leave sufferers entirely to their own devices.
I volunteered at a soup kitchen in Seattle for five years in my late teens-early 20's, and almost all the guests were older men. And almost all of them were veterans. I'd say about 1/4 of the veteran guests had been physically disabled and couldn't work, 1/4 had had their livelihood wrecked by the recession, and 1/2 had varying degrees of PTSD that in many cases led to self-medicating and a downward spiral. Most were on a miles-long waitlist for VA benefits. People see our veterans on the street and sneer. That some of them are on drugs causes even less sympathy. In any case, what I'm saying is that disability, both physical and mental, ultimately caused these men who served our country to be all alone, homeless, perpetually ill and destitute. Maybe there was never a "solution" for them, but there is help. A little goes a long way. But counseling is expensive.