i dont know if its for marketting bro. well it certainly helped boost sales when breeding and farming began. but the chinese have always believed in the superstition even before the arowana farms and sellers for the tropical fish markets emerged, back when early asian aro keepers collected their pets from the wild. its pretty old stuff. it may be used as marketing ploy nowadays but it certainly didnt start out as one
It is belevied by ancient Chinese that they are spiritual fish, and in the art of Feng Shui, they specificially state that it is good energy (chi-universal life force energy) , an entire house is arranged using mirrors, plants, lighting, bamboo for luck and animals. so the energy flow is right , etc. Fish are the one living animal still brought into the home instead of symbolization. I read my first book on it AFTER I got my aro, was coincidentally reading this book on Feng Shui, well the first page I opened it to stated every home shouse have an Arowana, also known as an ancient dragon fish were not just luck but bring beauty and grace-but they were a soul. It's good luck to have an odd number of fish. If a fish dies, it should be replaced, it took misfortune or death in the place of the owner. (one aro is enough, just 9 fish total, or odd #)
I think it's a way of living in some cultures, and a choice in ours. Feng Shui is also ancient Chinese art form kinda zen the house look pretty cool with mirrors, waterfalls, mini bamboo but for it to say the "arowana" so specifically and for me to open that book and read it literally the same week I had a "what kind of fish-marijuana?" dumped into my tank, the first page it fell to in a 150 page book? it was cool and weird.
This could be exploited by some, the aro trade, but for the one's who are born into those beliefs the Arowana are absolutely revered. It's really quite beautiful but reading all the fish rules is kind of cool. Not all Feng Shui books talk as much about Aro's, there's quite a variety.