Level 1-3 players, or crews composed of players level 1-3 in a regular match, are actively choosing their matches manually. It used to be in the bad old days before tutorials and level locking that everybody was thrown in together, and the debate about stacking that followed led directly to level locking.
The other thing is new players who come up through the level locked matches don't usually come into contact with more experienced players for obvious reasons and may not have formed an objective opinion of their gameplay skills.
I believe the two situations feed off each other.
What is then left to each player is to decide when a game is unfair, but I will point out that the first situation has been cited as just cause for stacking in previous discussions about it in these forums. For my own part if I feel that a game is unfair I will do something about it.
I acknowledge stacking is a problem but some times I don't have the mental energy or patience to put up with inexperienced players. Once you have been on a very well run ship/team it is hard to watch people play at a less than optimal level.
Part of my gametime is given over to training new players, and when I'm not doing that there are times I just want to play. There is nothing worse than having a run of really bad matches that you know you could win but the disparity of where you crew/teamie needs to be and where they actually are is just to great to deal with in 1 match. Or two. Or three.