Dehydration is the most common cause of eggbinding(on an otherwise healthy individual) this is most commonly caused by improper nesting. The holding of the eggs for periods of time longer then normal causes the females to test their physical conditions. They hold their eggs until then cannot hold them any longer, hence the depleted appearance of many females. Normally with proper nesting, they do not look depleted.
Consider, nesting is of prime importance to snake species, they each have particular and repeatable method of where and how they nest. And of course, this area of their biology is commonly ignored and misunderstood.
Of course their are many other causes, like scaring the the oviducts from infections(protozoan and bacteria). These cause the eggs to adhere to the walls of the oviducts. Cheers