Because there are tons of old anthologies and books about the history of women in sf, but they’re out of print; and nobody has been putting out new anthologies of classic sf that have really made the point.
Sigh. I don’t know if that’s a happy or a sad sigh.
Yes, it shouldn’t be necessary, but yes, it’s good that somebody is doing it.
Do I think that some of the crazier “feminist forgettery” folks (who’ve been saying “women never were able to make a mark in sf because oppression”) are going to learn better? Not really.
But that doesn’t mean the merely ignorant shouldn’t get a chance to learn and have fun with our fannish forebears! More cool stuff for all!