makes sense. Her audience is very wide, and she covers a lot of ground musically.

exactly!
I hear so many other reasons when to me it has always seemed obvious that this is why

My answer would be that she doesn't have a large loyal stanbase
but she always puts out quality songs, that attract people later on
that initially weren't checking for her.

I agree, today I played TTS for a Rih fan, and she wasn't feeling it...she says she wants TTT or PIU Rih.

she usually gets the GP on her side..she doesn't really have that loyal fanbase like Beliebers or Monsters but millions of people who like her, but aren't really interested in waiting to purchase the single first minute it comes out. They usually hear the songs when they start picking up on radio/online, then buy them and that's how it spreads .. that's what I think.