I doubt most experienced people would even want to attempt to keep / breed them, usually it's just those with a little knowledge who think they can do it...
Few people would want to spend the $20,000 (or whatever a purpose-built walk in fridge room would cost - probably more come to think of it) and few people would actually want to work in a fridge on a project which would never allow them to make any money or even give away any babies they produced.
However, it is easy to understand how people might misunderstand the situation and think "Why don't they just let private keepers have them?" when they don't realise how specialised the species' needs are. I know when I first heard about it all (about 10 years ago), I had the same thoughts at first.
For many species it is entirely correct though, the best way to conserve them is to freely allow private individuals to have them.