If you have an accident that requires you to quickly remove yourself from the vehicle, there's a good chance that your airbags will have deployed (right into your face), your seatbelt may have locked,
Seatbelts don't "lock" they may, if newer car have "pre-tensioners" that fire to pull the belt tight. To be sold in the US the belt release must be able to be released under full tension.
I have tested this (unfortunately) in a roll over. I ended up upside down being held in place by my seatbelt. I was nauseous and felt sick from the rolling G force, but merely had to release the belt in the normal way and fall to the roof and crawl out.
In all my driveing, it was the one "total" I had, I also was a tow operator way back when and saw the results of not being buckled in.
I remember the 1st seatbelts, my Dad installed them before they were mandated. You had to lift a buckle, much the same as aircraft belts are or were the last time I flew commercial. Car belts today just require you push (not pull like the old ones) and they pop loose.
Air bags inflate and rapidly deflate, likely before you are even conscious of what just happened.
If the accident is bad enough, most of the side windows will be shattered or blown out, making the tool not needed.
It isn't a pleasant experience, and one most will try and avoid going through again.