Does Your Product Sell Itself?

Today my doorbell rang. This is something that almost never happens. I opened the door to see a young girl with a wagon full of cookies. She said, I’m selling Girl Scout Cookies. That was her whole pitch. She assumes I know what they are. I do. She assumes that I understand she wants me to buy them. I don’t. How many products can you sell just by announcing their existence and that you are selling them?