That's why MC manages everything in the library. Although desirable, there is no real need for writing tags to the files and some users here run completely tag-free files with no problem. Besides that, there is probably no standard for video and image files, e.g. MC has its own proprietary way of tagging jpg files, which is completely useless outside of MC.
On the other hand you can easily export tag infos into Excel Sheets to use somewhere else. Unfortunately, most other media applications do not allow to import tags from text files or Excel Sheets. At least I don't know any.