Finding quality writers can be an issue to, but Zatanna's last series was amazingly written by Paul Dini and it only lasted 16 issues or so.
Female readership in comics has been dramatically growing over the decades since when I first started collecting, the problem is that the data doesn't specify what type of comics they are reading.....and I would gander that super hero comics is not their first choice.
So at the end of the day it's about business, if female lead comics sold more, than DC would publish more.