Why? If they were any good they would be in the system already.
Well, "good" as judged by watching park football, where a dozen players may all look all right, and "good" when put under pressure, in a big competition, on TV, with players like Taumololo running at you, are different sorts of good.
If a player steps up at some time, it is noteworthy, particularly in a big competition. Maybe the fact that the players now have something to really play for, or now have a quality coach, is helping them lift.
But the fact that they may not have stood out before doesn't negate the fact that they are doing so now. I think the NRL clubs should be interested in good world cup performances.
But you are right that anyone who is already consistently performing would be in the system already. I'm just saying that 3 or 4 top efforts against top teams probably qualifies as coming good for some of these players, and should be looked at.