1. Different use case: trying it out it reminded me more of a Slack/IRC/bulletin board than anything else.
2. Different framing: it uses a public square (Twitter) framing (follow, follower, channel) instead of a personal relationships framing (friends, groups, etc).
3. Too complex for casual users: this is kind of ironic because Scuttlebutt is modeled after real life interactions but in a way it ends being too complex with pubs (public and private), long and cryptic user IDs, etc.
These are some reasons but there are more. Happy to discuss them.
The big problem is how to fund a social network that doesn't rely on selling it's users data, IMO.