Why does Keybase client download user avatars to my local filesystem?

I've just noticed that there is a folder called avatars under ~/.cache/keybase (on Ubuntu 18.04) which is currently 265 MB and has avatars of 4,623 users. Is there any reason for doing it this way?

Keybase version is 3.2.2-20190412141809+5262f90fd9

The issue identifies the ~/.cache/keybase/avatars directory, Ubuntu 18.04, and Keybase version 3.2.2-20190412141809+5262f90fd9. Start by locating the avatar-cache behavior and reproducing the reported disk usage; done means establishing whether this caching is intentional and documenting its rationale or expected retention.

Written by the indexing model from the issue text.