Why aren't the rest of the URF skins on sale?

I was really hoping that the Soraka and Nami skins, as well as that guy who's Definitely Not Udyr would be on sale too, preferably for 25%+. And that the other URF related skins like Urf rider Corki, Fisherman Fizz, and the Warwick skin (Sorry I can't remember the name) would be on sale too. I convinced myself to spend money on this game for the first time ever in order to get that Definitely Not Udyr champion and Secret Agent Xin Zhao, now I'm 175 RP short...