Customary?
It's mandatory.
I have a buddy that flies - he was a flight instructor when he was pretty young. He recounted the time he was with a big Iowa football player at the controls. The kid froze up and wouldn’t take his hands off the controls - my friend tried removing them but the kid was just frozen in fear (they were diving towards the ground). My friend punched him in the face and freed the controls just in the nick of time.
“I landed the plane walked to the office and quit my job - I wasn’t getting paid enough for that crap.” (I think his next job was as a crop duster!)