User blog comment:Jimeee/Skyrim 1.9 beta update adds Legendary difficulty and raises level cap (Updated Apr 8th)/@comment-68.42.246.83-20130322162330/@comment-5469467-20130323025633

I imagine that the ability to remove perks that is unlocked at the end of the Dragonborn DLC is aimed at players who want to redistribute their perks in a tree without having to reset the skill by making it Legendary.