I believe that onboarding is a complicated part, there's a lot to learn and a lot of expectations are generated and must be controlled in a calm manner. I think a lot of people go in thinking they're going to make "a lot of money", just by posting and we know that's not the case, it's a long road for things to settle down, so this knock on the return is also a point that scares new people away from hive.
I also hear a lot about "having to write" to make money, it seems that people also create these ghosts or maybe it's just laziness, they'd rather risk their money in a betting shop than have to write and build up an asset little by little. In short, there are a lot of challenges and a long way to go to adopt Hive.