When I first tried darktable I tagged everything because it was available and it somehow scratched some kind of OCD itch I had (I guess). But it didn’t take long until – for me – it was more effort to tag than the benefits it provided. That’s nothing against darktable, just a reflection of my workflow.
I don’t shoot huge numbers of images, I don’t shoot events / people, family or otherwise (although I’ve been occasionally tempted, if you know what I mean! 
), I store everything in dated descriptive folders and after processing (and after backups run) I delete all images that weren’t “keepers”, keeping only raws, sidecars, TIFFs, edited copies (GIMP, whatever) and since they’re small, exported JPGs. Sometimes I’ll go back and delete TIFFs as well later on to save space.
So my workflow is simple:
- Copy raws from card to filesystem
- View / cull with XnView
- Process in raw editor
- Finalize in bitmap editor and export
- After backups, delete everything I didn’t touch
But I purposely don’t keep extra shots, so I don’t need to search for anything.