What's with all the towels?

So I went to the post office yesterday and the guy forgot to give me my change so he came to my house at 9:30 pm, gave me my change, bowed deeply, kept apologizing and gave me a post office towel. I couldn't BELIEVE he drove to my house to give me my change! So besides the question why does the post office have special towels, the bigger question is why are towels always given away. I have 4 towels given to me from 1) A bar named Anaconda 2) The dragonboat races 3) I don't remember, but it's blue 4) The Post Office. If this keeps up, I will have 9 towels by this summer. Who wants a towel as a souvenir?!