Its extremely valuable for debugging. When you've got a bug that is in a specific build you can collect the set of dependencies that produced that build and BAM you've got an env that should replicate the bug.
This is the best argument Ive heard for it. It's also an argument for my priorities of safer languages, development rigour, and use of vetification and test tooling. Each of these reduce amount of debugging one does later on top of improving reliability and security.
