Have you ever performed a Random Act of Kindness?

A good friend explained the philosophy of the random act of kindness. She is fond of paying for the car behind her in the drive through in the morning. I have tried this several times, it feels good and it’s a nice surprise for the person behind you. It sometimes carries on for several cars. Someone told me I was wasting my time and should be donating to people who could really use it. Am I wrong, but doesn’t the giving and receiving of a RAK not brighten your day?