Detroit's and Ken Holland's player development philosophy can be summed up in the following: The NHL is not the place for on-the-job training..... that is what the AHL club is for.
Detroit wants their young kids to learn how to be every-day professional hockey players in the AHL, rather than at the NHL level. Nothing is given, it must be earned. Roster players have the job, unless you take it from them. Over-ripen the player in the AHL, so when they do finally get their shot at the NHL, they run with the opportunity, rather than struggle.
Detroit also has a tendancy to draft the guys that have slipped down the draft for whatever reason.... these guys tend to either boom or bust. Allowing them extra time in the AHL gives them a better chance at turning out to be a boom, rather than a bust. For years, Holland had a habit of trading down on draft day. Instead of taking one late 1st round pick, Holland would trade that pick for two early 2nd round picks. Figuring once you get outside the top 10 players say.... is there really that big a difference in quality between a late 1st rounder and an early 2nd rounder? not really, so often times Holland would choose the two 2nd round pics rather than the single late 1st round pick. Again, using the one of the two 2nd round picks to go after one of those high upside boom/bust type players that other teams didn't want to take a risk on. If he didn't pan out, you usually had the other pick, who was a safer type pick to fall back on.... If they do pan out, you found yourself another Zetterberg, Datsyuk, Nyquist, etc... late round steal.