Dogfighting is not an end in itself, a fighter is there to allow something else to happen, shooting down a fighter is only significant if it means the enemy has fewer fighters and good pilots the following day, or allows your mission to succeed/theirs to fail. If the Japanese were attacking a target the Zeros job is not to dogfight but to stop the enemy taking out the bomber/torpedo planes, not quite the same thing. The Japanese suffered heavy losses trying to break through organised protective screens of fighters protecting a fleet, getting involved in a fight with the screening fighters is what the defenders want you to do, it stops you doing the actual mission you were sent on.