I normally don't give money. I very rarely work and live on a tight budget, surely I could afford giving now and then, but my excuses for not doing it do the job. If I ever make the money an average person makes I think I would give now and then but in no case every time I am asked. I would favour baskers over plain homeless.
I have been kind of and atypical homeless myself. I always preferred to sleep rough than expending my money on an expensive room. Working is much harder for me than to miss some of the common commodities for a while. I think it is all about the power games you find in work, difficult to take for somebody who has issues dealing with authority, so I don't last.
I used homeless facilities a few times when needing a shower or a washing machine, though I rarely felt welcome by the workers there me not being a homeless by their book. Sometimes the need of something is not enough and it looks like you should feel pity about yourself and/or be an alcoholic or yunkie. They don't like people who are actually choosing. In my experience volunteers are always nicer and less judgmental than professional social workers.
I travelled a lot and met different kinds of homeless. We cannot generalize on that.
I have seen all the range, from authentic scammers to people with bad mental issues. For example in the UK I had a close friend who was begging as he preferred it to work, he was making around 10 pounds and hour while I was making 6. Not mention about Christmas, in a good spot then you can make a fortune, crazy amounts of money. He had to put much less physical effort on it but more psychological especially related to social stigma and the others homeless he had to deal with. For the record, he was a bad alcoholic and drug addict and died.
I have seen real mafias of Romanians conquering all corners of North Europe and fighting among different factions for the control. The people who hated them most where the Romanians who went to those countries to work as they suffered their social stigma. Heard stories from those which said the one showing a photograph of their famelic offsprings, owned a mansion back home.
I have seen people in India blinded or amputated probably for mafias to work for them.
I have seen people borrowing puppies or kids to get more money.
I have seen people with not much option to stop their cravings than that.
I have seen a lot to have a clear idea.
It would never cross my mind to beg, I know I would feel like shit doing that and I probably become and official beggar (monk?

or kill myself before that. I think is a hard job and really psychologically damaging. I think is a job by the book, in the section of not socially productive ones, in fact you get professional beggars working for charities, paying people to hunt for charity, that's fucked up. I would never get into giving money to those. The business of making you feel good about yourself.
Sometimes I think giving money to homeless keeps them in the situation as they can keep on like that. Even some become homeless as in their map of the world that's their best job opportunity, it is craziness. It is really complicated. Charity is quite important for humans, and I believe is as old as us. But I feel some people gets damaged by it, as they could do much better feeling the need to solve their problems. The richer the country the more the ''poor people'' complain about their situation, it is like we don't complain about the situation per se if not about the difference of our situation with our neighbour. I as well think society is getting more and more competitive and individualistic and those features create isolation and defeat. Easy to point out at problems really difficult to find proper solutions.