If the suppliers had them, if the importers thought they would be popular, if the wholesalers would pay the cost for them which is considerable per fish if only a few come in due to the quarantine testing and risk of losing the whole lot if a certain percentage die, all the way down to would the shops buy them at that price right down to whether or not the customer would say 'well I wanted them but I'm not paying that!'
Not being negative here and you possibly know this anyway but shops and wholesalers have been stung many times in NZ by customers wanting and then not buying ie zebra plecs.