* Headers that are originally private, but are later changed to public * Headers that are intended to be public, but then are changed to private * Headers tha

* Headers that are originally private, but are later changed to public * Headers that are intended to be public, but then are changed to private * Headers that were created in the very early days of the company, which are so deeply integrated into everything that renaming them is basically impossible (or at least very hard and risky) * Headers that are set by some appliance/third party solution not controlled by CF, but which are technically internal and must be stripped. * Newly acquired company has its own set of internal headers. Management is not amused when a huge, disrupting refactor is suggested by engineers. And this is just a tip of the iceberg of possible problems when your scale is big enough.