Another example: my partner is left-handed, I am right-handed. We dabble in instruments together; we have a right-handed bass guitar, and an electronic drum kit we set up in a traditionally left-handed way. Both very doable, but there's definitely a debuff when learning from someone else. We're very monkey see monkey do.

I think the "sharp weapon" hypothesis is interesting and favors "why right and not left?" but I think it's too specific and unnecessary to explain the more important "why 90-10?".