No need to guess, that's a fact
This could be elaborated on... especially concerning
conditioning fish. Many newly imported fish will only accept live foods, and good vendors will take the time and patience necessary to ween fishes onto easily offered and purchased prepared frozen, and sometimes, dry foods. Aforementioned good vendors will (read:
should) also hold fishes long enough to determine if fish is carrying any ailments, and can treat for them beforehand. Conditioning fish and acclimating to captivity will drastically improve hobbyists chances of keeping fish long-term,
and the time put into fish is directly seen in cost of fishes. There's a reason a yellow tang can be found ranging from $20-60... go for the $60 from reputable, non-price-gouging, vendors.
With that said your point still holds true, and no one should skip QT :thumb: A shipped fish is a stressed fish, and throwing it into your display tank and hoping for the best is not good for anyone/anyfish.