Yes, there's a very good reason for removing your hand from the thrust levers at V1. However, while you may be perfectly open to learning and may never need a raised voice, some do.
I'd be dead today if I stayed a quiet, meek, nudge-em-gently type of pilot. One need not carry on a routine conversation by shouting, but every bit as much as distractions, suggestions, pauses, questions, and other techniques have their place, shouting does occasionally do the trick, and may be very well necessary to jog someone back to reality. If you haven't found this to be the case thus far, with more experience, you may.
Some years ago I found myself in the right seat of a Learjet with a newly minted pilot who required a great deal of supervision. He was given a clearance to descend, and an airspeed restriction to meet. He put out the speed brakes and retarded the power to idle. As I made the thousand foot call approaching the altitude, I noted that he showed no inclination to reduce his rate of descent. His airspeed was bleeding off rapidly and he showed no incination of increasing power or retracting the speed brakes, either.
After several calls of a normal-tone "Airspeed, Airspeed, Airspeed," it became "AIRSPEED, AIRSPEED, AIRSPEED, ALTITUDE, ALTITUDE, ALTITUDE." I pushed the thrust levers up, and he yanked them to idle. I pried his fingers off the spoiler switch and retracted them, he thumbed them out and clamped his hand down over them. Not consciously, mind you; he was locked into a slow-down and go-down mindset, and was otherwise unresponsive and staring straight ahead. I continued to increase the volume and the tone of my insistance as I used both hands to physically remove him from the controls and take control of the airplane. After I pushed him back in his seat, away from the controls, and a very excited ride-on mechanic who was accompanying us joined me in the cockpit to see what was going on, the catatonic pilot suddenly popped back to life. He turned and looked at me, and said quietly, "you don't have to shout."
We were in mountainous terrain, and descended well below our altitude. We were flaps up, and slowed well below our minimum airspeed.
Don't have to shout? Yes, I do. When the situation calls for it, yes, I do.
The thing is, from an instructor's point of view, I'll decide when that might be. Not the student.