I completely agree with you, in other words, we can say that cockfighting is simply a game for the locals, its a local game which does not need to be aired or offered up for betting on by the casino on a global scale, even local casinos have not picked up on such games, so its practically impossible for us to see such games on international casinos like Stake and the rest.
Cockfighting is more like a game that brings a small community of friends and family together to have fun, like I said in my previous comment, over here in Nigeria, cockfighting is not popular at all, only a very small part of the country engage in such games, most especially in the north, and its always in very small and local communities, the kind of places we call remote villages.
Any ways cockfight is almost as old as traditional gambling but is just that the game is very unpopular due to the risk associated with it and how many people are actually interested I going through all the hustle just to get a cock to fight each other, the game is not prominent and that why most times a lot of the games as relate to cock fight are mostly done at the tradition level.
You can't see any online contemporary casino listing such games in the catalogue and that is because most players will not pick interest in such games since it will be seen as an old school game.