The 10th best male rapper in the country is on a lot more people's radar than the 10th best female rapper in the country, and it has nothing to do with skills.

Mainstream radio pretty much has a limit of 2 female rappers that it will push at a given time (Bodak Yellow would've flopped hard if Iggy was still a mainstream darling), and the indie scene isn't that much better. Mello Music has only released 5 albums from woman, and 3 of those were either instrumental or remixes. I don't think Stonesthrow, Rawkus, or Def Jux have ever put out a rap album from a woman.

This scarcity means that it's much more difficult to stumble across more than a couple dope female emcees, and that the female perspective is a scarce enough aspect that it's worth giving it its own category.