I think it's because Carol is tied to many different things. She debuted in Mahr-vell's stuff. Then she became Ms. Marvel a title intended to make her Marvel's Wonder Woman as Lee and Conway admitted. Claremont wrote her there and introduced a lot of stuff in that run. Then she went into Avengers, and then had a stint in X-Men.
So that allowed for a lot of backlog to build up, and then Kelly Sue DeConnick and Jamie McKelvie changed the game. And in addition to her own title she's in Kamala Khan's Ms. Marvel, and then the Avengers books.