I remember in the original Wolfenstein 3D treasure counted towards your score, as did kills, and at certain amounts you could get an extra life. Since Doom, the idea of "lives" in id games has gone the way of the dodo.
In the "reimagined" Return to Castle Wolfenstein they have carried over some elements, perhaps for nostalgia's sake. Playing through the first couple of missions, I cannot see any gameplay benefit yet to collecting treasures in RtCW since there is no longer any score or lives to be had. Is it just for bragging rights, then? (The game is far too old to have achievements.)