It happens. I can’t say it’s super common, but even with the protection of the cartons, accidents happen. Hell, I’ve checked in store, and had an egg crack on the way home from braking hard. Only once, but it shows that the right forces in the right way can cause cracks.
I haven’t bought eggs in years now (yay for my hen!), but I’d see it maybe twice a year or so
I wouldn’t either tbh. Small car, great brakes, and I don’t speed. So when I hit them to prevent a problem, that fucker stops.