I think it should also be noted that many zoo's don't actually house their snakes in the display enclosure you see 24/7. Many are merely moved to that display during business hours.
im not saying that's good or bad, just wanted to point that out.
i was lucky enough to do an internship at Australia Zoo working with rescued animals that would be brought in, or removed from populated areas. You would struggle to see a more caring knowledgable and enthusiastic group of people.
im sure there are a lot of iffy zoos out there, but I don't think we should generalize. Just my 2cents