I think rescues have a lot of good reasons not to ship, not the least of which is that they're not dealing with people face to face. Rescues usually want to screen their adopters, which typically involves a face to face meeting. There's also the risk to the animals, which admittedly is minimal, but you never know what will happen when an animal changes hands within the shipping company. With the incredibly high numbers of reptiles flooding the market, there also is no need to have animals shipped, when there is an abundant supply of the more common species virtually anywhere in the country, and if people are willing to pay shipping in order to obtain a more rare animal, they are probably more along the lines of collectors than rescuers, and there's definitely a difference. People who rescue reptiles generally have a lot of red eared sliders and green iguanas, with a smattering of boa constrictors and burmese pythons, and a few large monitors. (I'm sure you know this, being in the field.) In my case, I only take animals considered too dangerous for traditional adoptions; namely venomous snakes or very large snakes. That's kind of been my niche for the last few years, but I never go looking for animals and I typically don't want them unless every other option has already been exhausted. If someone asks me to take an animal, and I know that I'm its best option, I'll pay for shipping or drive to pick it up if it isn't local. I've trucked a rattlesnake from Georgia to Colorado, although I didn't make a special trip; now I'm in Washington, and I haven't taken any new animals in the last year (and no trips to the hospital -- funny how that works).
The more I work with reptiles, the more I think that no one should keep them as pets at all, unrealistic as that may be. (I feel the same way about pit bulls, and I have 5 of them, also rescues.) The thrill you get when you see a reptile in the wild for the first time is totally lost when you see it in a cage; I like designing very natural vivarium type enclosures, but even so, it's a snake in a box. We (legally) import about 2 million reptiles a year, and who knows how many are illegally imported -- if it's anything like other exotic wildlife, maybe as many as 85-90% of the total, based on USFWS estimates, or somewhere between 13 and 20 million a year. Most are dead within 6 months, and that's not even taking into account the captive bred animals. I'm about to start ranting -- maybe I already have, so I'll stop before I get too into it.
I just read Animal Underworld, by Alan Green -- I highly recommend it. I knew most of the stuff that was in the book, but this guy names names, and I learned some things about a few people (zoo directors) I've worked with over the years. Not good things.