In reply to tehmarks:
There is one small advantage actually. There have been recent cases of passers by removing karabiners from fixed ropes that were in use by cavers in the dales.
It is now recommended practice in our club to use maillons for the top anchors that are accessible to anyone passing. A half-turn with the spanner stops them being removed easily, plus they don’t have the same appeal to light fingered types although probably make better key-rings.