yes homelessness is often complex and multifactorial. years of abuse, psychological traits, bad luck. Pick any combinations in any order.
I honestly don't know what homeless people need, if they even want to go back to 'normal' life. What I think is possible is helping the volunteers to do more with less to provide essential care (hygiene, medicine, basic nutrition and warmth). Then there's safety.. Even some free lockers would be a boon for them. Keeping critical stuff when you sleep is a luxury for most.
All I know is that with not much funding, a bit of space, and smart care (invest in the easy to save, make them volunteers, and grow ~exponential self sufficient resources that way) you could tame these problems by a lot. Most naive solutions (renting hotels) backfire in cost or quality. I was quite stumped after hearing guys saying they'd rather sleep out than in a shelter, in the winter.. I don't want to assume but it's pretty telling.