Kuso, I accidentally went back in my browser and lost my long reply... add this to the list!!1

Anyway, the (abbreviated) reasons I think kokonotsuba hasn't seen wider adoption are:

1. Hardly anyone knows about it
2. Not n00b-friendly to install and configure (compared to others)
3. Not 4chan/8chan-in-a-box - it misses many features, bells, and whistles that are expected on those types of systems, and that's what most new imageboard admins want
4. No proper release structure or easy upgrade method

That's not to say it necessarily should do all these things, just that this is why it's not the go-to imageboard software despite all it's pros