Most left handed people fall into the "functional ambidextrous" category. We can't do everything equally with both hands, but in a test of the major hand skills, we will do some right & some left-handed, whereas a majority of people that are right handed, don't do use the left for a lot of the major skills.
For instance.
I write, bat, throw, dribble, golf, left handed.
I use a mouse, scissors, screw driver, and play guitar all right handed, and it would drive me nuts to try to do them the other way.
Most of it has to do with what I grew up with. I had to use right handed scissors & guitar growing up, and that's all I can do now. The first golf club I ever had was a "leftie", and I can't use right-handed clubs to save my life. I wish my parents had just made me try their clubs, but they found a left handed club and taught me to use it. I don't golf because I'm too cheap to buy a set of left handed golf clubs, when everybody I know has piles of right handed clubs I could have for free.