yes i did once until you have more people asking for money cuz they saw me be nice to one

Depends on how they appear to me at the time. I saw an older man once, with his dog. They really looked down and out, but he was doing all he could to shelter his dog. That I could tell. I was very, very generous with him. Another guy walked up and smelled to high heaven of booze and actually said "got a buck for me, I need another bottle of something". I told him, "no way buddy". It all depends, eh?

This is very true, it's no ones place to judge others for addictions.
A lot of the homeless population suffer from some form of mental disorder, so they will turn to drugs or alcohol to try and cope with that stress. 40% of schizophrenics are found within the homeless community alone, and are either outcasted from their families because of a lack of understanding about their disorder or leave home during a break down or to not be a burden on their families. And many of the vets who are homeless suffer from PTSD.
Being under the poverty line it is hard enough to get the medical attention on deserves and theres a big sigma that those who are homeless are a burden on society because they "wont" find a job and juts spend their time drinking. Many cannot find a place to bathe let alone afford new or nicer clothes to go job hunting and are usually turned down applications when they try to find a job - i've whiteness this first hand.