because fans today have the luxury of watching their team and their team only for the entire regular season, so if their team doesn't make it to the series, they're just not that invested.
As an aside, I've gotten so sick of how BAD Joe Buck, Harold Reynolds et al are, that I'm muting the game half the time (unfortunately I haven't figured out how to sync the G's radio feed). I wouldn't BLAME your average baseball fan for not wanting to deal with that crap!