They are 7-1. You know why? Mainly because of SMART QB play. If you want to keep changing the play to a pass, you will end up making the game shorter, giving the other teams more opportunities, and throwing too much could lead to interceptions/fumbles/sacks/ and more 3rd and long situations.
There are times to change to a pass play, but sometimes even if they show that they are moving to a heavy defensive package, you have to stick with the play because a lot of times, they never bring house. Other times, they may crowd the line, so if you break through that first wave of defenders, you're gone.