Interesting topic, a USP for Hive in my eyes would be the ease of community building and the monetisation possibilities for that community. It's easy and inexpensive enough to start a Hive-outpost/community and create a token that is already integrated with the POB model.
Onboarding the users seems to be the hard part, I still think the hurdles of onboarding (and retaining) users are the downfall. Hive requires a lot of time and effort to be worthwhile to the average user, truly. Unless you have a substantial stack to begin with, you won't earn much, which detracts from the monetary selling point.
Ideally, we need a large community to adopt Hive as their primary platform and build upon it from there. If we could onboard some big games/franchises, with a fan base, then we can snowball easily enough. The blogging/video/image uploading, and of course, core blockchain features all come into play then.
So yeah, my USP for Hive is High value community-building potential.
RE: Why is Hive not growing?