That's very true. I don't care about ships in Harry Potter, but I always got the people who complained that BAM! Unexpected Ginny out of nowhere! I like Ginny as a character (for what we know about her) and I would have liked to see more of her rather than be told about her when she needed to be there. People care about Hermione because she's present in the story from beginning to end, and develops over time. Ginny seems static because she can't be there, and if somebody were shipping characters, I can see how she'd be easy to overlook as a possibility for the main character.