They're building out plenty of applications themselves. That's the right approach. PGP didn't unleash a whole new world for applications because it didn't attack usability, which isn't something you do with an API.
The only way I see us migrating away from our current gpg use cases is if all the integrations we use somehow went unsupported. There's simply no reason to assume the risk of inserting Keybase (or anyone else's) dependencies.
I'm willing to believe nobody in your corner of the world does. That's not the only corner of the world.
Obviously they want to lock users inside their tool for business reasons.