Probably because there aren't a hell of a lot of female superheroes to work with that have the potential star power Captain Marvel does - besides, they're working specifically with Carol Danvers, not some made up "female version" of the character. I imagine she'll wind up essentially playing the Ms. Marvel role, but Ms. Marvel might not translate as well as "Captain"
Is it a given it`s Carol Danvers? It could be Kamala Khan.
From a business perspective if I am Marvel I pick Khan over Danvers.
given her back story (and i had to look her up) wouldn't she be better suited for Agents of Shield?