I learned how to crochet from my grandma as a kid (like, kindergarten or earlier) and she taught me to hold my yarn with my left. Learning to knit, someone was trying to teach me to hold it in my right hand and I struggled sooo much! Went back to holding yarn in my left hand and knitting wasn't a problem at all. Still, 10 years of knitting later, I can't hold it in my right ¯_(ツ)_/¯ I didn't even know it was a thing that people did, but I knew it was the only way I could seem to hold yarn and needles at the same time.