I lost pretty much all interest in Piper, and a lot in the show in general, when they got rid of Jim from American Pie and it stopped being a "fish out of water" story. I was invested in the story of "can she hold onto a normal life being on the inside", but once that was gone I just became increasingly annoyed by her.
Luckily, other characters became more important and I continued to watch because of them..... but I never was as invested as that original storyline.... (Which is I guess why I didn't feel the dire need to be watching these last two seasons and am only starting now)