So many reasons, and opinions about the OP, I guess it really is different on how we look at it. But like @akram143 has said it must be a stage or process in which gamblers are being addicted through favoritism. And no doubt that both will just result on the same thing.
From my understanding favoritism will not lead towards addiction. Maybe some 20% might get into addiction through favouritism. Most of the gamblers just spend when their favourite team or specific players are there in the event. This will be available periodically, upon which there is low chance to get into addiction through favouritism.