[brsteg]

It's unfair to keep the lap cars in the order, not the other way around. Under green both the leader and 2nd and further back are all in traffic. Yes if the leader passes a few lap cars more than 2nd I see some argument for they earned those cars by passing them; but by bringing out the caution you are giving the leader clear track (taking him out of traffic) and giving him a car or 2 between himself and 2nd in those instances. That advantage is too large for the leader.
Nothing is worse than watching 2 guy go back and forth in traffic only to have a yellow and a car put between the leaders because it just so happened on the lap before the yellow the scored leader had just nipped a lapper at the line. (Saw this more than once, though I'll admit not a norm.)
If the leader can't take advantage of clear track alone, that's driver error or a fading car that didn't deserve to win. {These things aren't aero sensitive like wing cars, thank God, but open track to run your line and a little air on your nose are definite advantages}