Homelessness is a complex problem with many causes ranging the entire gamut from mental health issues, poor lifestyle choices,deliberate intent, inability to integrate after being institutionalized (either prison or services), or simply bad luck, to name but a few. Trying to make some sort of political argument out of it does zilch to address the problem. They were once called tramps but now the numbers have swollen and urbanization means they sleep in doorways instead of under hedges.
Did closing the old mental hospitals and moving to care in the community lead to a lack of care as one Labour MP stated?(Denounced as a Victorian relic by no less the the then Minister of Health Enoch Powell)
Does immigration add to the problem?
Is the educational system failing a swathe of vulnerable people?
Did selling off social housing accentuate the problem?
Is enough done to acclimatize prisoners and service personnel to life outside?
Do we require vastly more sheltered housing units?

What is certain is that modern life is increasingly complex and the less able(however you wish to define the demographic) can and do fall through the cracks.

http://www.trueandfairfoundation.com/content/file/feature/review-hornets-nest-report-into-charitable-spending-UK-charities-12-de

http://www.independent.co.uk/life-style/health-and-families/health-news/the-demise-of-the-asylum-and-the-rise-of-care-in-the-community-8352927.html


https://www.theguardian.com/society/2017/jan/25/number-of-rough-sleepers-in-england-rises-for-sixth-successive-year

I will cherry pick the above article for the salient point made:
A spokesman for the Department for Communities and Local Government said the government was investing ?550million to 2020 to tackle homelessness and rough sleeping.

"Homelessness is more than just a housing issue so we are now funding projects in 225 local authorities to help those people at risk of becoming homeless, already sleeping rough or those with complex needs, to get back on their feet."