I have a keybase account and don't really use it. I like the idea, but part of the issue for me is attaching my "real name" to various online identities. I've used different types of pseudonyms over the years and do to poor opsec, some of them could be linked to me using the pseudonyms I use now. It's nothing illegal, but also nothing I'd like others to know about. So to attach my real name to keybase, I'd have to reestablish my identity in various places. Doing that, of course, removes some of the trust associated with the keybase model.
Additionally, and I realize this is tangential to this discussion, I use pseudonyms to somewhat reduce my privacy "surface", so to speak. If I take my twitter, HN, reddit, etc, etc. and say "this is me", you could build a pretty decent profile of who I am (politics, hobbies, profession, where I live and so on). That's a different privacy problem than keybase is trying to solve, so no criticism is intended, but it is a problem for me.
I believe one of the creators had said it is okay to have multiple accounts to keep identities separate or even to have an account for each identity. It does make it far less user friendly to need multiple accounts and multiple keys though and introduces a larger chance of making mistakes. Especially if it isn't that important to you (and it doesn't need to be!)
I use KB as an easy way for people to verify my signed messages - not necessarily for sending encrypted messages to other users. Mostly just a "This is me, you can verify it is me at Keybase easily - as long as you trust Keybase."
Doing that means users don't need to install PGP and know how to use it to verify that I am me. It isn't important now - or hopefully ever. By making a practice of it, my users expect it. if I am ever compromised, the malicious actor won't succeed in fooling my users as I expect at least a few will try and verify the message and will see it doesn't verify.
For myself, it's about being a solution for a "what if?" scenario than anything practical or even privacy-related. It's just the best psuedonymous way of proving identity within some level of reasonable doubt that I know of.
Additionally, and I realize this is tangential to this discussion, I use pseudonyms to somewhat reduce my privacy "surface", so to speak. If I take my twitter, HN, reddit, etc, etc. and say "this is me", you could build a pretty decent profile of who I am (politics, hobbies, profession, where I live and so on). That's a different privacy problem than keybase is trying to solve, so no criticism is intended, but it is a problem for me.