The way I've been trained;
During take off, captain has his hand on the throttles up to V1, then removes his hand. FO then guards the throttles by placing his hand behind them in order to prevent any "uncommanded" movement. He keeps his hand there until climb thrust is set.
In theory, this prevents the captain from aborting above V1, and prevents him from yanking the throttles shut if he suffers from some kind of sudden medical condition.
After this critical phase I see no pressing demand to hang on to the throttles? If you disagree, then you should have your hand on the throttles at all times?