I agree that they are a bit disconcerting, particularly when they look like fully grown, healthy young men that could get a job. I can easily ignore those that walk up to my car at a light and stare in; I just smile and shake my head, no. But I will tell you that I have given food and self-cleaning items to some that frequent the area around where I work. A few of them appear to have mental issues just from the pattern of their walking and expressions. I won't give money but I am glad to guide them to a shelter if they need one.
I've been approached at gas stations more times than I care to remember; it always scares the crap out of me because they seem to come out of nowhere. There is one time, however, that I was in the Pearland area and a young man approached me directly and slowly and asked me if I could help him out as he needed to get back home to xyz. Due to his mannerisms and the fact that he didn't behave as if I owed him something, I said, "I may be able to help you but you have to be honest with me and allow me to ask you a few things." At first, he looked like I'd bopped him on the head. But when I just stood there waiting, he said, "Ok, I need money to get back home because I blew it on beer this weekend." I said, "If you knew you needed to get back home, why didn't you keep enough back for gas?" He said, "Because I'm stupid". I laughed. He laughed. And I put $5 of gas in his car. And told him to not be stupid and to remember me next time he has the urge to be stupid. He thanked me profusely and said I reminded him of his Mom because that was something she would have said. I was good with all that.