1. Most k-pop fans are teenagers and people in their early 20's. This means most of them are virgin which is a huge factor for the music the kpop groups produce.
2. Most gg fans are Male who are not confident about their sexuality and want to keep the image of masculinity before society.
3. Most bg fans are Female who tend to be jealous of successful women.
4. Most gg fans also have this agenda of feminism so if they stan a bg, it will make them look fake.
Point 1, 2, 4 are for why gg fans don't stan bgs.
Point 1, 3 are for why bg fans don't stan ggs.
Take all of this as an observation and an opinion and not facts. Also take all points as one and understand the context.