I am ambidextrous and as stated before I have used many sewing machines and they are primarily left handed. I had my left hand in plaster last year and thought I would still be able to sew. Noooo way even on the machine. Even pulling my knickers down so I trained the dog to help. I can right with my left but was taught to use my right which is better. One other job I hate using right hand for is ironing, much better left handed. This is a family thing write with right but use left for loads of jobs. Painting etc.
I learnt to use a treadle seing machine and when using one it is definately all left handed although I never thought about it until now. Interesting thought.