Reason I want to play a new game over again is to try out a different class/subclass and have at least tried every possible spell at least once to see what you can do with them in most unexpected way, along with that comes to see the exclusive dialogues related to said class or race and how you might end up on a different permutation I might have never had before, I know there is still a few of them I 've never taken myself into yet and my spare time to play the game is running away.
After having grown fond of certain characters, naturally curios to experience their dialogues from every possible angle as well, as simple as that for me.