Wholesalers I think have a huge part to play in this. Over here they stock so many species that you'd never recommend due to their final size. Some may be a bi-product of the food trade but most are because they look cute when small and will sell. The same thing goes for aggressive species like humbug damsels. They might be cheap, hardy and easy to catch but does the number imported need to be so high when there are thousands of better small community fish out there.
The average tank isn't massive, at a guess, I'd say 3-4ft so why is every shop rammed with tangs. I put some of this down to the wholesaler offering them cheaply and some on retailer and hobbyist for lack of imagination.