I've sometimes thought of the same thing: as a SS/HG writer, why do I write from Snape's point of view more than Hermione's? I did a lot of soul-searching and I realized that in writing Snape as a man in love with Hermione we get to dwell on Hermione's best qualities as a woman. Maybe we project what we'd like a man like Snape, or any other man, to see in us; maybe we put those qualities in our versions of Hermione.