Air Bag Not Deploy problems of the 2004 Lexus IS300

On July 18, 2008, I was driving my Lexus is-300. My wife and I exited the highway and stopped at a stop light on the off ramp. While waiting to proceed through the stoplight, we were struck from behind by another driver going approximately 50 miles an hour estimated by the police officer. The rear end collision was so forceful we were pushed into the vehicle in front of us. Our vehicle (Lexus is 300) is totaled - the backend completely crushed and front end severely crushed. Our front and side impact bags did not deploy. I received a major head contusion and was taken to the hospital. We would like to know why the air bags did not deploy and is this a common problem with this brand/make.