They had no idea how to care for the animal and were looking for the cheapest of everything and only the minimum that would be required to keep it from dying over night.
For example, if they bought a bird, they’d get the smallest bird cage in the store, no matter what they bought.They’d also buy the cheapest food we had, no matter if it was for another specie of bird.
People who would buy reptiles wouldn’t be willing to purchase things like UV lights or cages/tanks big enough for them to move around in. They’d only buy whatever the over-the-counter dry food is that they sell, which isn’t a replacement for fresh vegetables/fruit and live prey. They wouldn’t buy the vitamin supplements that the reptile would need, nor a book on how to take care of it. It was especially bad with cheap reptiles like Iguanas, Anoles, and Geckos. They’re cute and they’re cheap so people buy them on a whim, not realizing that they need to spend 15 times the price of the animal just for the initial setup, then another couple hundred a year in UV light bulbs and fresh food and new cages/tanks as they grow. (Very few people realize that the adorable little 6 inch long baby Iguana will grow to be 5 feet long and live up to 20 years.)
Don’t get me wrong, some people truly did know how to care for their animals and would do anything needed. But the majority of people just thought they were “neat” and wanted to get them and not give them the time, effort or expense required for a living being. They were little more than novelties or toys. I’d be surprised if a tenth of the animals I sold over those five years lived more than a year. And that year was probably a living hell for them.
A mouse or rat that is used to feed reptiles, large fish and even some mammals (Sugar Gliders are rather fond of a pinkie mouse every now and then).
Edited: Ferret Herder is on the right track. There are plenty of warning signs.