The feeling that the app is shady (because of permission overreach) may stem from the notion that Keybase is a chat app. It is, perhaps in the same sense that

The feeling that the app is shady (because of permission overreach) may stem from the notion that Keybase is a chat app. It is, perhaps in the same sense that a browser running Slack is a chat app. It also includes crytographic key management and message handling via both GUI and command line (the core product), as well as a FUSE-based file system interface that allows transparent encryption/decryption with other users (Keybase FS). Viewed in that light, the installation footprint might be considered more reasonable.