That's what happens on the road in a noisy environment. This is why you need to have HFA.
Notice Brady at home, yelling "52's the MIKE, blah-blah, Gronk, get back!, blah-blah..."
On the road he cannot be heard. It's all silent count. Everything that Brady sees through all his years of experience do NOT get communicated because it cannot be communicated, perhaps even in a HUDDLE. There is just the use of a pre-determined physical signal for snapping the ball. Of course it should be varied as much as possible, but defenders will have a huge advantage since it can't be changed often, absent a timeout.