Unclear why I need to install the CLI

Here: https://github.com/Azure/azure-cli-dev-tools#setting-up-your-development-environment

Asks me to fork and clone either azure-cli or azure-cli-extension, but doesn't tell me why I need to do that.

I'm trying to build an extension that I want to host in my own github repo.

It would be great to explain to the user why we are asking them to clone.