The short answer is because they can and want to. The long answer is in the faces of everyone whose lives they touch.
A couple of college guys began filming random acts of kindness, including giving $100 to each of a bunch of homeless people. And it’s not just money. They listen to their stories, hug them, and spend a few minutes with folks who most people probably try to get away from as quickly as possible.
What random acts of kindness have you done lately?
I think the important part of this is speaking to them and hugging them.