Tagging is work. Fiddly work that's surprisingly costly in effort if it's not trivially automatable stuff like time and date, location, application, and so on.

Tagging is work. Fiddly work that's surprisingly costly in effort if it's not trivially automatable stuff like time and date, location, application, and so on. Naming is hard work, but tagging means creating and choosing shared names all the time, with the pressure that the combination needs to be reasonably unique, otherwise you won't find stuff. Tagging is also fiddly if you don't have a really good bulk action UI. You can think of the user-controlled paths in a hierarchy as tags, and moving files is the action of untagging and tagging. By moving 100 files from one directory nested three/levels/deep to another, you are removing 300 "tags" and adding 300 different "tags". And you can rename the "tags". A single click and drag, 600 actions, and you can see the before and after trivially, and undo trivially too (at least in Windows). Tagging is more useful for ad-hoc "favourite" lists, and the occasional cross-reference (but it's work to hunt down the elements in the xref).