It does slowly happen. There's a new `nix` command (a.k.a. Nix 2.0), which has a better CLI, though it's not yet 100% complete, I believe. But already useful (e.g. `nix search`).
Does Guix have a better CLI?
https://gnu.org/s/guix/manual/en/html_node/Invoking-guix-pac...
Because it's all Scheme, Guix has well defined APIs for all sorts of things. For instance, there's an API for search paths (environment variables you need to define when you install packages), one to create application bundles, one to create VMs containing GuixSD, etc.
That, in turn, leads to clean CLIs in my opinion: 'guix package --search-paths', 'guix pack', 'guix system vm', etc.