First and foremost, because she's Tori.
I'm not your average Tori Amos fan, I don't own tons of merchandise and haven't read her biography yet. However, I know she's more than just an amazing musician and artist, she really really loves her fans. She's willing to give out so much to them, even at her own expense. What made that crystal clear to me was her willingness to stand under a scorching sun and pay attention to each and every fan waiting for her outside the concert theater. For someone who has been doing this for as long as she has, it's not a trivial matter.
Secondly, the incredible, heartfelt, touching, piercing, brutally honest, creative and unique music and lyrics she writes. I don't know how she does it, but she just shakes, rattles, squeezes and jangle jingles my heart with every note she produces.
I'm happy and honored to have known (and met!!!) Tori and her music, though the road to realizing how amazing she really is was long and bumpy. What's important is I got there and even managed to see her perform in my own country (another very nontrivial thing).
I really hope she comes back!