I think Airbus are trying to keep both pilots in the flying part of the loop. Which is laudable enough. But if I am flying manually and setting off drift to track a course, it is a right pain for both of us if I keep saying Heading left 3° Heading right 2° etc, just to centre the heading bug. Much easier for PF to click the HDG knob as required.
Lazy solution: "This is my best guess at the heading to lay off drift. I'll be within five degrees of it to fine-tune but won't need the heading bug continuously adjusted."
Lazier solution: "I'm going to fly TRK/FPA".
Laziest solution: "I'm going to stick the green track diamond over the top of the ILS dagger."