Once they're comfortable in their current state they can work on improving it. You can't focus on learning new skills or searching for a job if you have to find a blanket for tonight or you'll freeze to death. Almost everyone isn't going to hire a homeless bum, so they need enough stuff to make themselves not look homeless. They get those things as handouts on the street, from picking through the trash, or from robbing people.
The problem is that when we give them money for begging, they go use that money for a little bit of food and a whole lot of whatever it is they are self medicating with. Change is uncomfortable and doubly so for someone who is a substance abuser. There are charities who help people who want to get off the street and your money is much better spent there since they can help more effectively by providing food, clean clothing, a place to stay and help for whatever emotional problems or mental illness that made them end up on the streets to begin with.