Reptiles react very poorly to being rehomed? Where is that info?
Snakes generally don't care who owns them, as long as the husbandry is close to correct. I've never ever seen a snake pining after his first owner. Same with 99% of other reptiles.
People usually "swap" and trade reptiles because the animals don't care who owns and feeds them. If you're breeding and at a certain point you no longer need a certain snake, and someone else does need it, why not switch out and both of you have new animals that you can use in your breeding programs? The snakes don't care who's name is on their cage. As long as they get their rat, the person holding the tongs doesn't matter.
I'd ten times rather see a person who needs/wants to get rid of a pet GET RID OF IT. If you're "tired" of your dog/cat/horse/guppy/snake, then you're way less likely to continue to take proper care of it. Giving it away, selling it, taking to the humane society... all prospects for the animal to find a new home with someone who does want it. The same applies if you have something in life happen where you need to get rid of the animal. It's better for it to go to a chance for a good home, than to stay just because some random person might judge you for not being a "forever home".
Most people won't advertise a pet for free on craigslist because certain people continually tell everyone that ANY person looking for free pets is only going to feed them to their snake/use them in dog fighting/kill them in arcane rituals/send them planet X/ or whatever alarming situation MIGHT happen. So they put a "rehoming fee" in to prevent a new owner who will only want it because it's free, not because they actually want the animal.