Conducting such games carries the hallmarks of cruelty. So not everyone will support such games. It can be administered temporarily in places where it is practiced according to tradition, but it is better not to encourage. But these games are difficult to add to any casino or gambling.
For me, I will say that this game is far more better if allowed to be played local, and not what could be had on casino or any gambling site, due to it's tendency of having a short duration and lifespan of cock. Because I'm sure for an individual to be able to gamble on such game, he/she is ought to have a clue on the strength & weakness of each cock, to know which is capable of performing better in a fight, which all those can never be possible within the short life time a cock has to stay before death
Horse racing is completely different because there is no chance of harm. It is supportable.
And not only that, but the fact that a horse has a long lifespan (i.e 25-30yrs), as compared to cock (i.e 5-10yrs), that alone is good advantage of people organizing a sport around it, since with such period, any user should be able to know the strength and weaknesses of each horse to know which best to gamble on base on past previous performance, unlike in the case of cock that has a short time frame.
Aside the lifespan thing which you are talking about, which personally believe to be one of a valid reason why such game should never be on a global gambling casino, another valid reason which have been actually discussed multiple times is the fact that in several parts of the world, anything that could cause any kind of harm on an animal is considered as animal cruelty, and we know that before a game like cockfighting to go into global gambling casinos, it first have to become a global game that catches the interest of at least the majority of the world's population.
And you and i know that, if cock fighting is considered to be animal cruelty in some parts of the world, global recognition of such game will never be possible, which also means that , global gambling casinos will never make such game available to gamblers for betting.
So for me, i would say that, we should just forget about cock fighting ever becoming a global game for the chances of this happening is very rare.