You may not notice the pound at the start of the hike, but once you are tired or maybe there's not water where you expect it to be and you're hot tired and thirsty, you would certainly notice it at that point if it was added back to your load. Part of that is mental though. Also if you have carefully evaluated your gear and are satisfied with what you're carrying, and in your mind you have sufficiently lightened your load, then you might enjoy the trip more.