I think a lot of beggars do it not just for the money, but because they like interacting with people. So it's good to acknowledge them. Nothing wrong with offering some food if it's done in a way that gives the person some good interaction. And, anyone could get tired of eating in the same places, so it can be a treat.
But money should absolutely never be given. My technique, instead of lying and saying "I don't have anything," is to simply say "I can't help you."
I think you're right. Often times people in the Tenderloin will ask me for the time. When I give it to them they say "Thank you" and move on, with no followup request for money or food.
It's possible they genuinely need to know the time. It's also possible they are trying to get me to take out my cell phone. But I think the most likely answer is that they want to have a normal human interaction.
But money should absolutely never be given. My technique, instead of lying and saying "I don't have anything," is to simply say "I can't help you."