To me it depends on the species. As far as I am cocerned, a lot (most) of snakes in the wild breed with a close group of others, be it their uncles, sisters, aunts, grandmoms, cousins... etc etc. Some species of crotes and even Mtn Kings are even closer in relation to each other (moms,dads,sisters and brothers), and have been doing so for generations and eons. Hard to say that they have been impacted in any bad way by their natural ways.
As far as breeding in 'pet trade' herps, they are far from a conservative stand point, as they have no big ties to their ancestors. You cannot really say that some of the corns out there are even closely related to wild populations, same with some boids and other common herps. They have been breed to everything and anything to pass on a genitic design rather than bred to keep a species as whole.....if that makes sence.lol.
I do not think inbreeding is as bad as it is for mammals as it is for herps. Most do not have such a large home range as lets say mountain lions. Inbreeding in mtn. lions would prove to be fatal, as for herps it is just a way of life. Take the Mtn Kings. They live their lifes in small rocky outcroppings, and usually stick to one area their whole life. They do not venture out to find new bloodlines to create 'better' offspring. Their mates are close family members, usually not far from them or even in the same outcropping of rocks. Even same clutch siblings. They do not depend on new blood to make a better gentic animal, it simply is not needed nor does it impact them in a bad way. As for herps with larger home ranges, they do mate within a larger group. Herps with larger clutches and home ranges will also meet mates that are spaced further genitically, making it a wider bloodline, but still I see no big correlation with inbreeding in bad ways with them either. Just my opinion.....