Because for the most part it's taking far more time than most have been willing/able to spend on a video game.
To give some numbers: at a
sustained kill rate of 10 kills/h (which would be phenomenal), one would need to play 200+ hours in a single tour to get 2.000 kills. Actually, he would have to play even more, because no one is in a sortie all of the time. Aces high records only the sortie time (fighter, bomber, attack, vehicle)
In tour 234, the average total sortie time for the sampled 1070 pilots was 22 hours. The median total sortie time was 11 hours.
Only 31 pilots did put >= 100 hours into the game, one had >200 hours. (And we don't know if any of them shared his account with someone else, like a family account at home for example)
When I did my 2000 kill tour (I had a few more coming close), I accumulated 238 hours 'inflight'. That's a textbook case of 'no life'.
