Because it was an entire EP of songs, a la Animal+Cannibal or The Fame Monster.
For Beyoncé, this was also the case, and so I can't really say anything on that. Perhaps just album sales declining affected this? Nicki's and Katy's required the ENTIRE album to be re-purchased, and not everyone wanted to do that. Plus Katy's re-issue only had 3 new songs, one of which was already widely available as a single.