Getting users to tag data has already been attempted. Heck Office has had this built in for years (decades?).
We live in a world where after nearly 30 years of the folders paradigm, the vast majority of every day users still store everything on their desktop.
(Though IT policies are working to change this, forcing files to be stored on network drives and such).
Some more advanced users may use a folder called "work".
Years ago I went through and tagged all my photos. Of course the photo management system I used up and died. After that I gave up. I do have some photo organized and stored locally, but now days Google Photos handles most of that for me, including the auto-tagging.
When people sit down at a computer, they generally have a task in mind. Be it write a document, calculate with a spreadsheet, or send a picture of their dog to a friend.
Most people don't think ahead to "5 years from now I may want to find this document so I should think up of every possible word I may search for then and apply it as a tag."
Tagging data takes time, and a good deal of thought to have a coherent system. Then, technically, those tags need to persist and transfer across disparate OSs.
I personally love the idea of tags. My capstone project in college was exploring different UIs for tagging files, and trying to make the process as fast and friendly as possible.
But changing users habits is hard.