FoothillCoral, they are on the endangered sp list because of limited distribution, and if people didn't have them available they could not breed them in captivity. Should something happen to the wild population they will still be able to re-release fish back to the wild, also they can be bought as captive bred. They are not red listed, they can be imported with paperwork. The numbers of animals imported shows how common they are where they are found. If the habitat is destroyed and none were allowed in no more fish for hobbyiest or divers to see. I'm not in favor of over collecting or collecting in a way that destroys the habitat, but to say rare animals should not be available to people who want to care for them is just as bad.
Think of it this way, if any animal considered rare was not allowed in the trade, how would we get new species to keep? Who gets to decide what animals are rare? My example of the wonderpus/mimic stands, it may not be rare just the habitat it lives in is not normally collected so they just don't know. With that being the case how are we to learn how to keep them or possibly breed them (there are several sp of cephalopods being bred for research, food and pets). As I have said before, not that long ago all corals and most marine fish were considedered impossible to keep let alone breed. Who should decide which ones are common enough to allow collection and which ones are not?
Many of the species we keep, have limited range, look at flame wrasse, only found on rubble patches in over 100 ft of some of the hawaiian islands, should they not be allowed to be collected/kept? I'm not saying that wild animals should not be protected, but realize what they should be protected from. I sited a study in a PM I sent earlier and it is relevant here as well. Some research was done on some New Guinea reefs where they took all the angels off a section of reef. On another reef they did not remove any angels. within 3 years of removing the angels all of the species (even rare ones) had settled and recolonized. On the reef that they left alone only the most common species had juvs found habitat and settled. I'm not saying take all the animals, I am saying if you collect areas and protect the breeders or a potion of the reef (site study in Caribbean that said only 10% would be enough to repopulate naso groupers and the success they had with goliath grouper) and if habitat is healthy fish will rebound.
Just another thought to consider is how even the most common animal in our hobby got there in the beginning.
I understand what your point is just consider that others like me believe that collection is the first step in the long term goal of producing captive animals. I love pygmy angels and have collect colonies of 5 different sp so they might be able to breed. Fishers and potters have very limited ranges and now it is not legal to collect them in most of their range (yellow tangs are gettig expensive for the same reason) As the main Hawaiian islands are collected commercially by all those that used to collect the much richer northwest chain what will happen if we don't breed them? I have seen this before, what happens is called commercial extinction where it costs more to collect then you get for the animal. The population then has time to recover, but the individuals that are collected command such a high price that they are unafordable to the average hobbyist. People who love them and would give them the time to find out how to raise the fry couldn't affort them making them disappear from the hobby.
If you think less of a store that sells rare fish look at 2 of the rarest fish in the world. The cherry barb, common in every store is almost extinct in the wild because it was only wild on the island of singapore. The habitat was destroyed by man industrializing the island. What if someone had said don't allow it into the hobby, it would be gone because the habitat it lived in no longer exists. Same goes for whitecloud mountain minnows, they are found only in a small area of china, but people learned to breed them and now they will always be available. I know they are not the same as even keeping a salt water fish, but there are people out there who will put the time and effort into it because the animals are available and we find them appealing for whatever reason.
Again, only my own views.