Holy cow, that's a nice spell book builder! Where has that been hiding?
As for "needing" a spell book builder, I don't think anyone "needs" one, we just "want" one. It makes experimenting around with builds SO much easier and it also assures you that your points are accurate (I've made mistakes counting manually before, as I'm sure others have too). Plus, an online builder is something that some of us would like to have access to when not at home when you don't have the cards right in front of you.