Good point. If you are a non-professional first responding civilian at a collision scene, it's usually best to leave the patient where and as you find them, and leave the window breaking, extrication, etc. to the pros.

The exceptions are, in addition to imminent threat from an actual car fire, are if the patient's injuries demand immediate action to save life that cannot be performed in place, or there is a high risk to the occupants and rescuers from oncoming traffic, as with a wreck in the middle of a dark or foggy highway, behind a blind curve or hill, etc.

You might be surprised at how many secondary collisions into accident scenes or near misses I've seen, even with millions of candlepower of emergency lights flashing, cops waving down traffic, and everybody in reflective gear. Working a wreck on a busy highway or a dark, curvy rural road can be really frightening.

So the main reason for carrying seatbelt cutters and window breakers is SELF-extrication if necessary to escape additional danger, and only secondarily for those rare instances where immediately extricating someone else is essential.