Changes happen and it will be depends from the government to execute laws that can help to stop things like this, but the fact that we know inside that government there are many corrupt minds and it won't be hard to conclude that since we are still seeing places who continue to allow this kind of cruelty, it's either the government is not being alarm or there are part of this government who knows well if how money flows with this kind of gambling.
The fact is that many of the time, government in some countries have many things that remain unregulated and at that we have to understand that those countries which have no regulations concerning such things as gambling have open up the door for such activities that are outside some of the gambling rules in other countries that already have regulations in place, and one other thing is that, gambling I animals have been there for a while now, but people have only interest for those games that less risk and not too bloody for the unlookers.
But cock fight or dog fights are not popular because both animal have some element of wide behaviour that sometime could result into injuring their partners to the point of death without any regulation to prohibit that during the games.