I personally find the numeric id extremely valuable for internal data analysis and sharing. I can refer to rows by the numeric id, including a range of rows, and seeing the ids gives exactly that intuitive information about it's relation in the set that we are hiding from end users. Numeric ids can also be used for the same reason in an admin-only UI.
On the efficiency side, joining and querying by id is generally more efficient on CPU usage for querying, but you do have to pay the cost of having the additional column and index.
On the efficiency side, joining and querying by id is generally more efficient on CPU usage for querying, but you do have to pay the cost of having the additional column and index.