What does tagging add?

I tried searching by tags I added, but the search results were not limited to the songs that I tagged.

I don’t use tags much but…

you can go to “tags” under “your” stuff and then filter by tags.

Or if you search by tag you can toggle the "show only my library’ and it brings your tagged stuff to the top.

Do you mean Roon Tags or FLAC/MP3 Tags in the files themselves its a big difference

Tagging gives you quick access to anything you want.