I think you are looking at this situation rather casually. and it is a tired argument that is often repeated by many.
Here are some factors to consider;
- White Sox management attitude towards fans over the years
- Prices for tickets, concessions, and parking compared with other teams in the MLB
- Disposable Income (and changes to it since 2008), transit options, and geography of fans
The bulk of SOX fans are relegated to supporting their team from a distance, I would argue that many watch games routinely rather than pay outrageous ticket prices. I think you would be hard pressed to find the bulk of CUBS fans follow their team closer than SOX fans do.
Major things the CUBS have working for them are the years of SUPERSTATION brainwashing that WGN has done. This making them a team that is followed by a huge chunk of the MIDWEST, not just Chicago. When people from IOWA or KANSAS come to town, its for a CUBS game.
A good majority of CUBS fans goto the game more for the atmosphere of the park than the game or team itself. Many more attend to only partake in the frat like atmosphere that surrounds the area. CUBS games can easily be turned into an all-day event, the area around Comiskey still isn't inviting for the bulk of fans.
I am really too tired to put 110% into a response to this crap, but gotta believe I put more effort into a theory as for attendance than you have.