A bug is an undocumented feature
There’s an old joke in the software industry: A bug is an undocumented feature.
Some software is so beautifully designed with screens that are so intuitive that a manual just isn’t needed. I admire this kind of user-friendly interface, but it is not what keeps me in business.
Sometimes you must document software that is badly designed or buggy. When this happens, the tech writer is earning his keep.