One of the best marketing they can ever do is this, because while you may think Real Madrid is great advertisement spot, remember a team which is much smaller and do not have enough fans will also play against real Madrid too, and Barcelona, and maybe others. So you are getting cheaper pay, but you are getting good results anyway. Plus, why football teams? Well because football teams have fans that bet on football games, so when they see the shirt, and when they are not happy with their casino anymore, where do you think those people go? The company whose name is on the shirt. Also, these are not brick and mortar casinos, these are online ones, so you can reach out to the whole world.