Another example of the walled garden. You need their tool, whereas you can just use gpg with every other keyserver.
Maybe consider contributing to the effort?
Quick searched turned up several issues tracking the question:
https://github.com/keybase/keybase-issues/issues/327
Or if you read the issues you can see that there are some genuine concerns in there that you could help contribute to that would benefit the open source community as a whole, with the side effect of simplifying things for Keybase "as well". Primarily, from skimming, it sounds like the keyserver protocols are not as well documented and standardized as one would assume, running a keyserver from a fresh/new code base is a non-trivial matter with a lot of quirks/bugs to handle. So, who knows, maybe you could contribute to better documenting keyserver quirks, and pushing for better, less quirky, keyserver standards.
It should probably be easy to presume that if a user gives you their Keybase username they are telling you it's the easiest way to get their most up-to-date key(s) and revocations and that they are actively managing it. (Pretty much the same assumption any time anyone ever suggests to you a specific keyserver over just a fingerprint and keyserver roulette; that's probably the keyserver they actively check/update/revoke and will be the timeliest.)