I get the impression that the dual dialogue system was complicated enough to implement. I'm not sure how easy it would be to add in a lot more code to check things, and it would certainly introduce bugs.
That said, points in Sourcery do nothing now (eventually that skill will be locked at some point), and I think the decision to learn it might come up at some point in the main quest. That's when I'd expect Madora to strongly object.
I think that it's nice having your party members talk to you a lot around town. It's much more interesting than the normal followers.
