There are so many differing opinions and all have validity because each person on the street has their own story. each individual is different. Some would just as soon kill you because they have the chance when you stop to offer help. Others graciously accept what you offer.
I will rarely give to those who are obviously drunk, though I have purchased food and handed it to them after buying my lunch at a fast food place. The right thing to do is give them something to eat rather than helping to ruin their liver.
There are so many stories, so many situations that it is impossible to know them all or to attend them all. But look at yourself, how many of us have been by their side and we have not even admitted that they are there and are part of our day to day life. In the province where I live, the city has adopted many of them for their peculiarity and somehow they have ceased to be invisible and now one or the other helps them either with food or money.
There are so many reasons for these people.