I was always told the 50... 40... 30.... 20.... (and hopefully not ... 10...) calls are really designed to allow you to listen for the cadence and alert you to and sink/float you may not be picking up with the Mk 1 Eyeball. I found these enormously helpful when I was new on the bus. Still uselful on poorly lit runways without centre-line lights and in miserable conditions.
They also allow you to brace for a hard landing even if you have your eyes closed
