Rather than dog race, I play table tennis and even basket ball as these are easier to predict using historic data
Most time interest matters i will say since never put interest in it i wouldn't know it is that commonly unlike other gambling site. People interest are mostly focused on the well known games such as football, table tennis, wrestling, basket ball, poker, Roulette, Blackjack. But from most of the local gambling site i visit around my locality i barely find out people talking about them or even placing bet on that area.
I know for sure gamble preference is based on people's choice and interest. People would prefer popular games than games with no much attention to it. No doubt dog race is not common and popular because of the nature of it. It is not popular as others because no much casino picks interest in it and I have not really seen anybody talking about it too. May be this thread could be an avenue for is attention and popularity here.