Think bout it this way. There are loads of people who are struggling. MH, drugs, alcohol, low incomes, abusive pasts, disability, currently abusive homes, trauma impacted.
In a society with good supports, there are shelters, women's refuges, healthcare, counsellors, parents' supports, cheap housing and benefits. People muddle through, still housed. In a shit society there aren't. People fall out of housing. Then any trauma, addiction or MH is amplified, increased and self medication becomes the obvious outward sign. Coupled with housing being treated as a profit making asset, not a human right.
But if you kept the person housed, they'd be healthier, happier and, although not great, they'd be fine. Cheaper as well for the Tories at the back.
It's ideological. To have a big homeless population is ideology. We shouldn't blame the person.