There's no easy straightforward answer here.
On one hand, the primary task is to fly the plane and put the nose down with no delay and no interference.
On the other hand, given the strength with which the propensity to follow the FD is burned into our brains, its remaining visible is enough of an interference to the primary task, as to matter. From my observations, I can confidently guess that I use the FD by far the least out of my airline of 2000 pilots, and even for me, whenever it stays up because the other guy is too busy answering a radio call or whatever to change the dial the appropriate settings into the panel, it is extremely difficult to ignore it. Fighting the urge to follow it is a significatn distraction to the flying task.
Of course, one way to (at least partially) resolve this contradiction is for the PF to use his own mouth and the PM's hands to turn off the FD, leaving his own hands available to fly the plane. But then (if the story is told accurately) he runs into an idiot instructor who has taken it upon himself to reinforce automation dependency by forcing its use in inappropriate situations. It has literally become a taboo to not have the FD visible as its lack evokes a gut discomfort. It's somehow better for these people for it to be up and displaying a wrong command, than for it to be hidden.
For those strongly putting forth the notion that the FD is to be ignored, well... if wishes were horses then beggars could ride. We saw how that ended up with AF447 and the +8000 fpm FD that popped up in the midst of their startle and confusion.
For every child of the magenta that has flown a flyable airplane into a well publicized crash, there are hordes of ones latently plodding along without incident in normal operations, ready to make the same mistake when operations stop being normal. The mental conditions are there, just waiting for a trigger.
Last edited by Vessbot; 24th Jun 2018 at 17:19.