Being mainly horizontal cavers, they didn't feel they would miss that much. Several hundred dollars is a ludicrous amount of money to spend when few weekends training on the surface with a simple seat harness, knots and rack would suffice for the occasional pitches in otherwise horizontal caves. Probably a good idea that all vertical cavers are comfortable using knots. They can be really handy in a pinch. Difficult to tie and untie under extreme cold or pounding water conditions, difficult to pass knots and rebelays, pitch lips can be a real problem for an inexperienced knot climber.
Knots are good system for occasional vertical caving as an adjunct to mostly horizontal caving.
Many experienced vertical cavers in the Southeast US use very simple rigs for most if not all vertical caving. Not recommended for cavers seriously overweight. Die hard practioners of Texas use it for all vertical caving. Developed by the French for exploring very deep, very cold, and very wet alpine cave systems. Frog is a pretty good compromise between speed and comfort.