Terrific piece for TidBITS from David Shayer, who worked as a software engineer at Apple for 18 years:
Remember what I said about changes causing new bugs? If an
engineer accidentally breaks a working feature, that’s called a
regression. They’re expected to fix it.
But if you file a bug report, and the QA engineer determines that
bug also exists in previous releases of the software, it’s marked
“not a regression.” By definition, it’s not a new bug, it’s an old
bug. Chances are, no one will ever be assigned to fix it.
Not all groups at Apple work this way, but many do. It drove me
crazy. One group I knew at Apple even made “Not a Regression”
T-shirts. If a bug isn’t a regression, they don’t have to fix it.
That’s why the iCloud photo upload bug and the contact syncing bug
I mentioned above may never be fixed.