I carry the knife, in a vehicle it can get lost or pop off it's clipped location in an impact.
"Help, I'm trapped in a car!" plays out badly - if you are injured, you won't be able to do much. If you are still physically ok, just unlock the seat belt and climb out.
Now, go ahead, play out all the speculative scenarios, under water, jammed buckle, gas tank is dripping, immiment fire, whatever. Not. The #1 thing that happens is a collision with another car at speed, the air bags go off, you're stunned.
What will the knife do to help then? Nada. Sit quietly and don't make your injuries worse. Likely won't because you'll be unconscious.
For all those who want to weigh in with "What IF?" please do us the favor of citing the exact percentage of accidents that actually occur under those circumstances. I dare you to find any that are more than one digit before the decimal. I doubt you can, but if there are any, at least your point will have credibility.
You want to be a first responder, please take the training. Don't be the guy who screws things up even more and kills a survivable occupant. It will take awhile to get over that, and they never will.
