Rihanna even puts on a different colored wig each era, just like a prostitute does, as her handlers tell her who she has to become.
Anyway, Jewfro I was about to post in your ShitGa thread but it was closed

so here goes:
It wasn't offered during her peak because she peaked so early in her career that she was still so new.
Katy was offered the SB 6 years into her career.
Gaga didn't last that long.
Now, with her lack of hits, mainstream appeal and off-putting behavior (e.g., the vomit) it will never be offered to her.