Left-handers would naturally hold the bottle with their right hand and the corkscrew with their left, then turn the corkscrew anti-clockwise.
The problem is that corkscrews are made for right-handers and have screws designed to turn clockwise, so if you turn them the other way nothing happens! But turning it clockwise using your left hand is a very awkward movement as you cannot use the leverage of your thumb to push it. As a result, you will often see a left-hander hold the the corkscrew still in their left handed and rotate the bottle to make it work.
Our corkscrews all have reversed screws so they turn anti-clockwise, making it easy to open bottles left-handed.
Try leaving your left-handed corkscrew around for righties to use - lets them find out what you normally have to put up with!