I think as long as you've decided it's not for you, then so be it. We're not your mom. We don't now your personal situation.

Personally, I don't sweat it. I drive a bridge to/from work every day, only about 40 feet up. I'll probably survive a crash just fine. I'll get out. I have a knife like you. If not, well, I've never NOT seen a belt unbuckle, despite numerous car accidents that I've responded to. Worst case scenario? I pull out my car keys and use them, or the POS knife on them, to cut free.

As for car crashes and fire, again, not a very realistic threat. Most cars don't catch fire, blow up, etc.

By all means, if you've got the cash and inclination, buy one. Me, I'd rather not.