Those that can't afford cable to watch the CFL probably aren't attending too many MLB, NHL, NBA, or NFL games either.  And aside from Saturday night NHL games most people still need cable or some other form of paid subscription to follow teams in other leagues.

Most households still have cable or similar provider meaning that if they are watching the Seahawks or Bills they also have the means to tune into the Argos or Lions.  The fact that they aren't tuning in or showing up to the stadium has more to do with the product being offered.