Hardcore Cub fans stick there nose into the ass in front of them and go to games year after year, no matter what, for the experience. Hardcore Sox fans stay home.
Then you have the battle for the casual fan that goes to maybe a game or two each year. They can't name more than a couple players. Some years they may skip a game and go to a museum or some s%*#. Many of those fans will go to a suburban stadium no matter which team is the home team.
The hardcore fans for either team? They will b**** if the other team moves into their neighborhood and never visit except for a crosstown game.