I don't think this thread was about stigma. It was about whether thing called homelessness can happen to otherwise functional people. Whether such a thing exist.
The thing about what you call hardcore homelessness is the serious mental health issues many of those people have. And that is much bigger harder issue.
I do get it. When people think about homelessness, when they cast a ballot, we don't want them to think about the "hardcore" (as you put it) unsympathetic homeless. We want them to think about the more relatable people experiencing transitional homelessness. People who are leaving an abusive situation, people working a job that didn't cover their rent, etc. The Rosa Parkses of homelessness.
And that sucks. It sucks that the "hardcore" homeless are so stigmatized that the only acceptable way to talk about helping them is to frame a larger problem in which they can be hidden away as an unrepresentative minority.