It's pretty niche (and hacky). My use case is debugging CI runners by connecting to them via a reverse shell [0]. I want to manually run CI commands, but my reverse shell drops me into a new process without any of the same environment variables available to it that are made available by the CI platform to the runner. So I wanted a command I could paste to quickly inherit those environment variables and run the CI scripts that depend on them.
[0] https://github.com/milesrichardson/shonion