I've only had my seatbelt latch jam once (in 30 years). I was sitting in my carport and jimmied around with it to get it loose. This was a case of my sticking the belt in catty-wampers (hard to picture given the thousands of times we do it, but it happened).

It was only once, and a no-stress situation, but the thought of it happening while the car's on fire or upside down in a ditch kinda spooked me a little. I carry a Res-q-me on my keyring (in addition to pocket knife/ multitool) now and keep one in the DW and DD's cars.

They'll probably never need them, but they humor me, and I feel better. They love me enough to humor me...