I worked in housing for some years, including interviewing people who presented as homeless. The reasons for rough sleeping are very complex and varied. For some, a bed sit or flat would be enough. The ones who lived reasonably 'normal' lives prior to family or relationship breakdown or redundancy can probably pick up the pieces fairly well. But I've seen resources used on some, over and over again, where the responsibility of a tenancy is just too much, as soon as intensive support is reduced, the situation breaks down, and the person is on the street again. Alcohol, drugs, and the biggie, poor mental health all contribute to homelessness, as does lack of family support.
There is a project in this city that helps homeless people with food, clothes, showers, medical and dental services. They help people access housing, but not everyone wants what is available. They survive on donations, and every year people fill shoeboxes as Christmas gifts for the homeless, and have sleep outs to raise money. There is affordable housing in northern parts, but if someone has been evicted with substantial arrears, they'll find it difficult to get anywhere unless they are classed as 'vulnerable' only then do local authorities have a statutory duty to find them accommodation, which could be a hostel or a b&b.
The proportion of non UK citizens that are homeless is also contributing to the rise in numbers, especially in London.