If Rise wasn't sent to radio then thats probably the reason, plus its not really what the GP expects from her.
Oh, did i mention its not an official lead single?
Because both are not smash material. But at least Katy has the Olympics so it'll be fine for her but for Britney, it's going to be a one week top 20 hit on the charts and then gradual decline next to Pretty Girls' grave.
I think it's because mostly stans bought them so far. When it's playing over all the radio stations and official music videos are released (I think Katy is releasing a second video), then the casual listeners will pick it up.