Allowing the meat to rest and settle (about 5 minutes for chicken leg quarters) keeps it juicy and tender. When meat is cooked, the heat tightens protein fibers causing the juices to collect in the middle part of the meat. If you cut the meat prematurely, the juices that have collected in the middle will pour out before having the chance to cool down and for the juices to settle and distribute in the meat. Meat continues to cook when you take it out of the oven, so it's important to let it rest and cool down.