Well, for me animal fighting is not fun and should not be use as tool for gambling. But if it's not prohibited by the Government, these people won't stop using animal, because as you've said it's fun for those who are engaging themselves in this kind of activity. Anyway, in our country, cock fighting is quite popular especially here in our place. Many men elders are taking care of rooster as business (they sell it when ready) or use it for fighting for their own satisfaction. We have an arena where cock fighting is held, it's legal. Recently they even had a promotion called "fastest kill" and the prize is $600 plus a brand new motorcycle.
I it happens only in my country. But it turns out that many other countries have the same customs. In my area there are also cockfighting enthusiasts. But I don't know for sure if they gambled or just to raise the price of their chicken because they managed to win.
In addition there is indeed a merchant who owns a farm near me. DIa offers the chicken a lot on various social media. The chickens he sells also have the criteria of good chickens that are commonly used for fighting. If this had become a habit, it would seem that it would be difficult to cross this habit.