A fuel tank is not a pressure vessel (apart from being sealed to keep fumes in). If you get a puncture in your gas tank, it doesn't immediately and violently explode, it just leaks fuel out. Even if it does catch fire, it would not be as violent an explosion as a pressure vessel failure. In most scenarios it would burn, but not explode.

Fuel is necessary to the function of the engine. If cars didn't need it, they wouldn't have it. We've figured out C4 pretty well, but we don't stuff the doors full of it.

These thrusters could maybe help you if you fell down a particularly short cliff. Otherwise, if you get in an accident severe enough to send you rolling, you do not want high pressure nitrogen tanks right next to your head.