I have seen several frontal wrecked vehicles that did not deploy the airbags. I found some interesting info on the internet concerning airbag deployment. An algorithm is used to determine if an airbag will or will not operate during a frontal crash.
Real world crashes typically occur at angles other than directly into the front of the vehicle, and the crash forces usually are not evenly distributed across the front of the vehicle. Consequently, the relative speed between a striking and struck vehicle required to deploy the airbag in a real-world crash can be much higher than say a barrier crash. Because airbag sensors measure deceleration, vehicle speed is not a good indicator of whether an airbag will deploy.
What this all boils down to is that the airbag computer, using all the information fed into it during the crash, determines whether or not an airbag will deploy. I learned something today. Thanks for your question.