The majority? Uh... I strongly disagree on this. Unless you can show us data to support this, I'd have to call bs on whatever source you heard that from. It's probably attitudes like this that prevent more of the homeless from getting ahead from being helped. Plus please remember that there ARE homeless who drank/gambled/whatever their lives and homes away but there are also homeless veterans who can't get a fair shake no matter what.
I also have a big problem when homeless people get generalised into all being poor and homeless because they're all drug addicts and alcoholics, as if people stopped and actually spoke to them, they'll find that's not the case at all.
Helping those who are in need are everyone's obligation and responsibility. Those poor people should be helped by those who can but helping might have several definitions. For some, helping might mean giving the person some money, while for others, helping means giving the person a job. I would go with helping the person by giving him a means to earn money than just giving him money which will in the long run not help the person.