Terry being Bruce Wayne's assistant is just a cover story, but this is Bruce Wayne we're talking about; do you really think he doesn't expect Terry to actually do what he's expected to do? Yeah, Bruce covers for him sometimes, does the job instead when nobody else can see, but if he creates the cover story of grooming Terry to take over then he's damn well expecting Terry to learn how to do so. So Terry has to go to meetings and stuff, and take on ever-increasing responsibilities there as well.