My Mum thought when I was born I was a lefty, and knowing all the hassles she got when she was young about being left handed, she taught me to be a right hander. I now do everything with my right hand except when I use scissors, have to use my left hand. I guess she didnt teach me to use my left hand to do that when I was young as when I was young it was too dangerous for me to use them!
When my mum was a kid, many years ago she would be hit over the hands by teachers for using her left hand, was seen as a very bad thing and she didnt want me to go through that.