This is mainly due to the lack of maintenance in nixpkgs.
`google-chrome-{beta,dev}` depend on `chromium{Beta,Dev}`'s version
info.
`chromium{Beta,Dev}` are rarely updated and explicitly blocklisted by
`hydra.nixos.org`, meaning they are almost always outdated and not
cached in `cache.nixos.org`.
`chromium{Beta,Dev}` were intended to fix the build derivation of each
new major release (if something broke) *before* stable reached that
new major release.
Allowing for fast bumps in nixpkgs, especially if the stable bump
contains very important critical security fixes.
Something that can easily be replicated by using an early-stable release
or by manually entering a dev/beta version string in stable's
`upstream-info.nix`.
This resolves exposing end-users to outdated and vulnerable
`google-chrome-{beta,dev}` and `chromium{Beta,Dev}` versions.
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