As far as I know, mtimes are never used in any pipeline that uses are for dealing with program code, and probably that is one why the `-D` flag was introduced (as this usage is the most common usage of `ar`).

In the same way file permissions are ignored by compiler/linker pipelines, and they will only matter if you extract the contents. If you do that extraction as part of a compiler/linker pipeline, you will again not care about maintaining those - it's just that `ar` (a file archiver like `tar`) was "abused" for combining object files because it was already there.