many of us "practice" as a away to have fun but also to become more ethical hunters.
-while its true that you, and most of us as a generality could put one in the x ring at 200 yards, under normal deer hunting conditions, but thats in your "comfort zone", think about when you see a trophy buck one day but the shot is just a little bit different, or somehting isnt 100% normal or controlled as you are used to, and you miss. smooth move. thats why.