Would most people like their lawn service company to write "thanks!" at the end of EVERY bill?

I usually mow my own grass. Occasionally some-one may come by and help. And I usually say thank-you because I appreciated the help. So I guess you should say thank-you for your business to all your customers. However I guess I don't understand the amount due? If you just mowed someone grass, they should pay you, when you finish the job. Otherwise you might be working for free.