That's largely because they don't know (my god, first post and I'm probably wandering into a big flame war. Oh well.
). Shipping and receiving of fish isn't really open to the public and they'd have no idea just how those fish got there.
500 neons in a shipping styro.. Acceptable if they're handled properly. I consistently throw up my hands in exasperation when I'm handed a box with 50 plecos to a bag with about a liter of water. Do trans shippers just not get it?
(If intro is necessary, yep, I do the LFS thing and have for several years. Most of the tropicals we get are trans shipped from Singapore [or THROUGH Singapore, anyways])
Here's an article with a little more weight than the links provided in that thread:
http://www.petfish.net/painted_glassfish.htm
I respect Dr. Burgess as one of the sources used and I expect many others would as well.
Now just to throw a little gas on the fire...
I'm on the bandwagon that fish dying is cruel. The argument that "the fish doesn't feel anything" (better than "it's just a fish" or "fish don't feel pain" imo) is hollow and dodges the issue. Maybe I'm arguing a less tangible point than the fish huggers, but it's immensely disrespectful to life itself to inject shiny colours into it to promote more ignorance of aquatic life.
The aquarium *industry* really only cares about shipping units and turning a profit. I've yet to see any truly consciencious faces higher up. Once you leave the retail level (or very, very often before that) the interests of the welfare of the creatures you keep comes second to turning a dollar. I suppose an argument relating pet keeping to slavery could be made and debated, though it would be much more fun to start it at a PETA convention (or a dog show).
Getting back on track.. We create artificial fish (you know what I mean) in order to draw people in to buying aquariums and fish and food and carbon and biological supplements and all sorts of pricey miracles, but we do it to turn a buck, and not encourage a naturalistic approach. If people ('people' = 'the masses') were truly interested in maintaining and nurturing a slice of life inside their home, they would make a slight effort to research what they were doing and maybe even set up a nice biotope. Instead, people are buying tiny tanks, too many fish, fluorescent ceramic skulls, purple plastic plants, and bubbling treasure chests to stuff into a corner of their house to toy with. Maybe I'm just being a tree hugging old fart, but I consider that disrespect.
The point of whether or not dying "hurts" the fish aside, we take things from their natural habitat for the sole purpose of letting them be stuffed into artificial boxes for people to amuse themselves.
Of course, by that logic, if I build a 8000 gallon reef with surges, moving lighting to simulate sun movement, etc, etc, I'm no better than the family that buys 20 replacement neons from Walmart every week to throw into a bowl.
I dunno, bottom line for me (and I apologize if my argument is so disjoint.. I've had to come back several times to try and express myself the way I'd like to) is that dressing up the fish is just condoning and encouraging abusive fish husbandry.
Maybe I'm just nuts though.