good question. She should be one of the greatest stars. Maybe because she is not a usual pop girl, she has her own mind (I'm not saying other popgirls don't have but she always speaks her mind out so freaking loud)... But still, she has tons of fans, especially in Australia and Europe.
It's because she's giving this lesbian/boyish teas. You know how the pop world adores SEXY and SULTRY (Brit, Rihanna, Xtina and Katy) stars and she's never been like that or projected her way to be like that.
She deserves credit because she is such a great performer but still you know how it's like in the music industry visuals come first.
Because she treats herself strictly as a musician, not a popstar.
Her music, videos & live performances **** on the others girls. And she's still one of the biggest after 12 years. I'm not mad at her being underrated.