This is a very valid point, and something which makes me angry whenever I think about it. In many places, the musicbrainz db is built in a very clean way, but those artist fields do not make much sense, in particular the recording artist IMO.
Release artist makes sense. To state the artist(s) which are credited on the front cover. Track artists would make sense if they were used in the same function (state who is (prominently) credited for each track), but the guidelines instruct us to use them in a different way. Recording artists are totally needless IMO. Relationships are much better. And if some tagger software really needs a recording artist string, we should design the relationship framework to build one from the given data (like adding a checkbox “important artist” to the performer relationships, which is used for selecting the artist for the “recording artist” string).
Concerning classical music (fits also the thread How to help people with classical editing?): The artists issue was the biggest obstacle for me when I started editing classical music. To memorize the strange rule “Release: Composer; performer – track: composer – recording: performer” which just feels arbitrary and needlessly complicated. As I said, release artist is fine. For the (questionable) track and recording artists: Why not at least use the same rule “composer; performer” for all? It’s unnecessarily hard to memorize the strange rules, and additionally it’s not so easy to get everything correctly into the database. The best way (without using scripts which is something we should not expect from newbies) is first to set the track artist to the performer and push that change to the recordings, and then to change the track artist to the composer without pushing. Isn’t that insane?