To me knowing the CLI is a little like knowing how to read sheet music. It makes analysis and collaboration a lot easier.

You can put down a sequence of git invocations in a text file or script, stare at them, reason about them, tweak them as appropriate for your use case, copy and paste them to another developer, write about them in a blog post, include them in a README.

It's harder to do this with a sequence of gui actions.