Lack of awareness.
Considering the RH nails, I spent quite a long time in India and in such countries you will realize the importance of delegating some tasks to RH (eating, giving money etc.) and just some specific tasks to the left (toilet, touching shoes etc.).
If you try to give some money with your left, they refuse and do not accept it..
A kind of subconscious habit was formed and now I automatically use my left hand for the tasks where the RH nails would be in danger.
"If you want to discover the Universe, discover your Self." Gautama Buddha