there really is a chance that it could be the case. Why show your hand against inferior opponents that you can beat with 25% of your playbook, right? It's infuriating as hell sometimes as fans, but it has worked for the past decade I suppose. Hold the cards close until it REALLY matters.
***it also helps when you have one of the best QBs on the planet and he can run as well as a lot of RBs for other teams...