Good points. There are also herps that have such a high market value (or breeding value, or are simply uber-rare in captivity) that throwing money at their vet care makes more sense than for the average bearded dragon. I would hope keepers of those animals would have accounted for these costs without need for insurance, but I wouldn't be surprised to see counterexamples.
It is weird that reptiles are a luxury item that attract a lot of people who aren't remotely financially set to keep them. My most recent case was someone who bought a rosy boa from me ($375 with shipping) and let me know 8 weeks later that the snake wasn't eating because she didn't have a heating pad and couldn't afford one (snake had been on a roughly 10-day feeding schedule). She finally got one and the snake ate 4 months after she received it.