Nothing does. All it does is cause people to fly scared. Get rid of it.
Not necessarily, dying after long flights causes people to fly scared. Timid flying mostly does not give you a good score unless in a tempest. Most people run becuase they don't know how to defend and end up flying planes that can escape easier. This effect puts more people in fast planes to counter. Faster planes = slower fights.
Score doesn't accurately measure skill. Take a minimal amount of sorties in vulch mode, with only late war monsters and a good score awaits.
Getting kills in a Hurri I should count more towards score than kills in a F4U-4 - if you want to use score to indicate skill.
Adding an ENY/kill category to the score would help, except for planes like the Yak-3 with their overly generous ENY values.
Only vulching for score is actually pretty risky. I wouldn't recommend it. Keeping a top 5 score the entire month does take skill and understanding of the game. The current score has many metrics that factor in ability. And gives players a chance to score high even if they can't play all of the time.
I do agree with you about eny/kill. It would add a great metric. if vracui's theory is correct, it would mean players would have to fly mid-early war planes to achieve a better score. Which would tie into my presumption about too many late war fast planes.
I would also suggest taking K/T out of attack score... No reason for that in attack mode.