If you yank a package from the Ruby Gems repository, it can't be automatically and easily installed by the Ruby toolchain, used to build software that integrates with, in this case, Chef. You have to get the source by hand - except you can't, because the Github repo was also removed.
No different to pulling software from the Debian package repository, and yanking it from wherever the code is hosted, eg: Github.
Why do dependencies in this manner, so automatically? Well, that's the modern way. Python, Rust, Ruby, Go, whatever you're using, the libraries you pull into a project have their own dependencies, which have their own dependencies, and you don't want to be merging updates by hand into each of them.