It would be pretty worthless anywhere out of reach, if the goal is to put out a fire that is going to burn you alive (or give you enough time to break free). Unfortunately then you run into crowding issues where the extinguisher is taking up leg room on the passenger side.
For the case above, I don't think a single extinguisher would have been enough for that fire, and in a crash, if you have fuel leaking onto hot parts, I'm not sure how effective a single extinguisher would be in that situation either (of course having one and being able to try is better than not having one).