I never give any money to panhandlers directly, because I don't have time for DD, and money can cause as much harm as it can cause good. Once had bought a 10$ MetroCard to a guy in distress, who was clearly intoxicated during the night, robbed and left on the steps of Lorimer St. station.

There are many articles on this topic, one quite popular and easily comprehensible English article is from BBC: https://www.bbc.com/news/uk-37492659
Very generally speaking, it is extremely important to help those people to be better integrated in the society, instead of enabling them to continue antisocial behavior. Talking to them, assisting them to open about their real problems, motivating to ask for help with employment, education, healthcare, housing etc. is more important, than just giving money (the heck would it help with?!).

Much better approach is to give regular donations to charities and non-profits representing your causes (like Wikipedia, RSF, a local foodbank, Khanacademy and and others in my case).