Team wins and losses - very important
Pitcher wins and losses - not very important
Why should a relief pitcher who pitched 1 inning be designated as the game winner? Why should a starter who pitched 5 innings be the winner? It's a team game, that's the bottom line.
Once upon a time pitching wins and losses did mean more, when starters were routinely throwing complete games. But even back in 1968, you can see with Gibson and McLain that the W-L records didn't match up with the ERAs. Gibson's record should have been much better than McLain's and instead it was much worse.