Cock fighting is a kind of gamble that bet is placed on the two cocks whereby if cock A wins all cock A supporters wins. It is a legalize gamble in some part of Asia
You're right this type of game is what has been evoke since the early days in gambling when there have not been any digital technology with gambling during that era, not only cock but gamblers also make use of other animals like rams to gamble in those days, this were best enjoyed on an open field with a numbers of spectators to witness the fight and also cast their bet, cock fight is as interesting and same way entertaining and gamblers still practice this type of gamblings till present days all over the world but common in the remote regions under rural settings.
Many audiences enjoy cockfighting and using other animals because it is the entertainment they rarely find on the field or in public. The local government may allow the show as long as no one knows that they are betting because it can make ordinary people curious and finally participate in the bet. And yes, cockfighting is still practiced in rural areas, especially in Asia, because people are still used to betting on cocks or something there. But hopefully, in the future, the government will take action to make its citizens aware not to use animals to bet.