Seriously, what's the fun about cock fight game? it's animal abuse and that's not fun at all.
It's sad to see a cock that doesn't did anything wrong being forced to fight with each other until of them them sick or dead, while the owner will just looking for new cock again. I think any countries has a law about animals, if you see someone do this game, you can report it to police and they will arrest this dirty people.
I guess their motive is money. Maybe if you want to know directly you can ask them. Just watch them bet on their chickens. Then if their chickens win of course The price of their chickens will go up, they can earn more money.
My country banned cockfighting, even the police have arrested some of those activities. But it doesn't stop either, it seems that it is already a disease that is difficult to get rid of. Or maybe they've even bribed the police into keeping quiet.