Not meaning to trivialize your experience, and I'm sure that's true for a lot of projects. But on the other hand, big enterprise and government tend to accumula

Not meaning to trivialize your experience, and I'm sure that's true for a lot of projects. But on the other hand, big enterprise and government tend to accumulate projects that were written over decades of change cycles. Porting something like that across a non-backwards-compatible version bump while preserving identical behavior which is sparsely documented and uncovered by unit tests? Starts to be a serious amount of effort quickly.