A big part of this also stems from the fact that until 1998, the Brewers were an AL team and never played the Cubs. I know tons of people who like both the Cubs and Brewers (as weird as that seems now), because when they were growing up and through their parents' generation, their AL team was the Brewers and their NL team was the Cubs. So, you have scores of longtime Cub fans, whose family rooted for them long before the Brewers even existed, living in or extremely close to the Milwaukee market. After all, who beat the Brewers in the 82 series? The Cards...and who is typically considered their biggest rival? Yup, the Cubs. It was actually pretty easy to root for both the Brewers and Cubs for a long time because they didn't have a competitive history and they shared hatred of the same other clubs. I try not to get too ticked off about it, because frankly the proximity to Chicago revenue and Cub fans is as big a reason as any why the Brewers are still in Milwaukee. Prior to Miller Park even opening, I remember Bud Selig himself and other Brewer PR reps sitting in the Cubs' broadcast booth during Cub / Brewer games as the ballpark was being built talking about how great it will be for Chicago Cub fans to have such a close opponent to their backyard - particularly with a stadium that basically guarantees no rainouts. I even recall some mentions of how Milwaukee was still sort of a Cub town during that timeframe, since even interleague play really hadn't taken off until the late 90's, the Brewers just starting off as a NL team, and they were in the midst of an extended period of being a MLB afterthought without a clear path towards contention.