When you have a quarterback who is really popular with fans and people think he is a winner, but in reality he is nothing special and should be the back-up. He is allowed to play so that the fans will shut up about how they know none of their players by name, and to make games a lot more lopsided so they get a better pick in the draft and can actually draft a good quarterback.
Football Fan #1: "I am so glad they let Tim Tebow start now!"
Football Fan #2: "Enjoy it while it lasts."
Football Fan #1: "What's that suppose to mean?"
Football Fan #2: He is just a Tebow Placebo. This time next year, he will be old news, sitting on the bench yet again"