I am left-handed too and when I was at MQX a couple of weeks ago there was a scissor company there and I asked him if he had any left-handed scissors. Of course he only had one pair that was way too big for me to use but we got to talking and he said that when a left-handed person uses a right-handed pair of scissors they are going against the blades for the way that a right handed pair was made. Because we have trained our brains to use right-handed scissors and to make them work for us, when we go to use left-handed scissors it is awkward because our motor skills part of the brain is already trained to make the right handed pair work the way we want them to. Left-handed people that use right-handed scissors will go through more scissors than a right using a right and the same for a left using a left because again, we are going against the blades for the way the scissors were made. Does that make sense?
To answer your question-I don't use left-handed scissors because I find them just as uncomfortable to use as right-handed scissors, but because I have always used right-handed scissors, that is all I use.