I don't use a bench very often, preferring slung up prone or sitting when shooting a hunting rifle, and bi-pod prone with my target rifle. What you do frequently, is what your muscle memory will follow, so if every time you drop into a shooting position, your hand is under the forend, your rifle will always have a soft forward contact point regardless of whether you drape yourself over a dead fall, a rock, a snow drift, or a sand dune. What you always do is what feels natural. What feels natural results in a faster shot once the target has been acquired. On game, the faster the unrushed shot can be made, the surer the shot will be, due to the open ended timing you face with any live target. He might stay in place for a moment or for several minutes, but usually there is no way to know, baited game notwithstanding.
So what of the importance of removing as much human influence over the rifle during sighting in as possible. Well what of it? On the surface it sounds like a good idea, but if you sight in off sandbags, a mechanical rest, or some combination involving a bi-pod and sandbags, and the resulting zero is not in coincidence with the zero you fire while holding the rifle, I don't see the benefit. Accuracy matters, but groups size, other than their affect as a confidence builder or destroyer, does not. The accuracy that matters is the deviation between your intended point of impact and the actual. Learn to call your shots. Shoot pairs, cycle the action at the shoulder, and reacquire the target as quickly as possible after each shot. After the shooting, measure your shot string - measure the distance of all your bullet holes from the bull, then divide the sum by the number of shots fired.
That will pretty much dictate what your performance in the field will be. But when shooting game, you are emotionally connected with your target, and that too will effect your performance. The key here lies in your ability to disassociate yourself from the target when shooting. One way to do that is to focus solely on the mechanics of the shot: position, breathing, sight picture, and trigger control. You can only do that if you always concentrate on those basic elements of marksmanship when shooting at inanimate targets. If you are in the habit of shooting from a bench, none of those elements impact the results on the target, so you don't even think about them. From this we can see that removing human influence from our shooting isn't necessarily helpful.