Because currently the only female tournament available is ESWC, and in order to compete you need to be invited for. This invitation can be unfair, and in order to create a fair competition there needs to be a tournament where any team can attend and compete. Just ask yourself, how can you determine the real winner if only 8 teams are selected to compete, without a qualifying tournament?
Having a female tournament will help garner sponsors, donations, and most of all exposure. It will boost female gaming and encourage ladies from all over the world to strive to be the best.