Long answer: The item you need in order to respec is rare/hard to get/cannot be obtained until you've cleared the game on normal once. From this thread (http://www.gamefaqs.com/boards/633261-dragons-crown/66798319):
From: KIRBYSIM | #120
Can you reset skill points or are you choices permenant?
There's an item to reset skill points. You first obtain it by clearing Labyrinth of Chaos Floor 3. Gonna try to see if I can get more of it by clearing it repeatedly.