Specifically speaking, when big high speed fish takes off on you, the handle does not go flying backwards. You never get whacked in the knuckles, you never have to try and figure out where the handle is when it does stop burning line off so you don't have to take your eyes off what the fish is doing. I'm sure we can all survive without them, but they are really nice on a seriously big fast fish. I have not heard the term 'Surgeon's reel' in a while, but they have been called that because of the finger protecting aspect of the reels.
You can only see about 2/3's of the reel in this photo, buy it's my big Penn anti-reverse reel. I Love it.