Actually, according to a study done by USA Hockey and Hockey Canada, the biggest deterrent to continued participation in the sport past Squirt/Atom (9-10 year olds) is the time commitment. Usually this occurs if there are multiple children (lot of running around and schedule conflicts, snafus etc) or the schedule of games is too heavy (two or three games a weekend) or the travel distances are too far.
In addition to this, and this comes from having talked to parents when trying to recruit youngsters to the Learn To Play program, kids either prefer to be couch potatoes watching TV or playing video games etc. (they were at the rink because the parents were trying to get them to explore sports or activities away from the couch) or have waaay too much going on in their lives (multiple activities like tutoring, music lessons etc.).
That said, I agree economics is the primary factor in keeping attendance levels low during the regular and post-season, followed by our own time commitment constraints/distractions. (DVRs and lots of shows to catch up on) If it isn't us (the college hockey fan) it is our significant others (the non-fan) who, through a process of guilt (either direct or implied), require our presence while catching up on or participating in other "events."