Nothing drives this brutality home more than the introduction of special kill animations. Depending on your weapon, the enemy, and the fight conditions, your hero may execute a devastating finishing move that extinguishes enemies with a stylistic flourish. “You end up doing it a lot in the game, and there has to be an energy and a joy to it,” Howard says.
http://www.gameinformer.com/b/features/archive/2011/01/24/skyrim-building-better-combat.aspx
I think they are just trying to make combat in Skyrim more interesting than the previous "swing weapon at enemy repeatedly until dead" mechanisms that were employed in Morrowind and Oblivion. Plain and simple. Don't over anolyze this, it is mainly an aesthetic feature to compliment the re-vamped combat, magic and stealth systems and I, for one, view this as a welcome and refreshing change for the better.