Anyway, the answer is Rihanna. From 2007 until 2012, she was one of the biggest forces in pop and the #1 album is the one thing she was missing.
Katy's lack of Grammy's only started becoming apparent last year when she ended up being the biggest popstar worldwide and stans realized she hasn't won a Grammy. She also lost both her nominations this year, so it became a bigger deal. Plus, very few people, even within stanbases, care about Grammy's, so a #1 album is bound to be more important.