It is a big commitment and folks who don't find enough value in the game who quit do so understandably... again, fees suck, can't find worth in paying them then why would you?
Going along with that, the story in TOR also take a big commitment considering it's spread over 8 different classes... which again, is why I understand why folks choose to quit after they've played through one class. For them, that's the game and that's it...
The two biggest complaints people have about TOR is that it has fees and that it isn't the way KotOR should be. The next step down seems to be that it's too much of a commitment. All of these are understandable points to make. Fees suck, no it isn't like KotOR, if it were we'd have KotOR III and then people would complain about that not being the way they wanted it to be instead, and finally it does take a big commitment to actually go through all of this content.