The other day I found this article which said left-handedness is actually more common in men than in women (23% more common). I did some more research and discovered that while it may not be by much, the difference is still there. Naturally, that made me think of the Alethi women and how the Alethi's belief of not showing the left hand seemed illogical. Here's what I've come up with:If there are more men in the 10 or so percent of lefties in our world, one would expect to be the same in Roshar. We already know that the number of lefty Alethi would be low since it's a minority thing and unless a person's parents are both left-handed, the likelihood they're left-handed is pretty low (<20%). This does depend on Roshar resembling Earth in how handedness is passed on and works.
So the main point: the concept in Alethkar that women using the left hand is immodest could work because there wouldn't be many women disadvantaged. And if they were disadvantaged, it would be a small enough percentage so much so that it could simply be dismissed as basic clumsiness and lack of coordination or fine motor skills.