Like others have said, needing to cut a seat-belt in a vehicle due to the buckle jamming is rare. I have cut 1 seat-belt on an actual call in my Fire/EMS career. In that one case, I cut the seat-belt because I couldn't reach across a VERY large patient.

I can see a use for a specific webbing cutting tool in aviation and combat where expedient victim removal is often necessary.

...Splinter removal tool, on the other hand...