I think it's dumb as hell personally. You're addicted to the thrill of the gamble most likely, not the animals fighting to the death. I agree that it's animal cruelty as well. Maybe anyone engaging in the activity should be thrown in a cage and have to fight to the death, then maybe people will find something better to do with their time than watch animals kill each other. Gamble on something where death isn't involved.
Unfortunately, my friend, there are more than a lot of people who like such "fights" and bet like crazy on them. And sadly, I'm sure that if you put 2 people in a cage to fight till death, it will have more success than animals. I'm 1000% against any of these "fights", and I would never support them in any way. Even if the "fight" is between 2 bugs.