Because you're not a baseball fan or cause it wasn't very good?
I'm not a huge baseball fan, but I am not a huge boxing fan either (at least not until I started watching MMA) but I still really enjoyed The Fighter. When I was a kid, both my step father and real father were baseball fans so I sat
through enough baseball games (at both Yankees Stadium & Shea Stadium) to know the sport. My step father even tried out for and made a major league team but he did not play. He tried out as a pitcher and they offered him another position. He really just tired out on a whim so he turned it down as other things were going on his life. It has been years since I've been to a baseball game, but I would enjoy going again. I just think that watching baseball on TV is boring. For TV watching I much prefer football.
I guess the quick answer to your question would be, I'm not sure maybe I was just tired. I think I will try it again when it hits HBO and I don't have to pay for it.
On a side note for you Mark Wahlberg fans, I just went to IMDB as forgot the name of the movie The Fighter and it turns out Mark Wahlberg was the Executive Producer of Boardwalk Empire!