Addressed in the article: on each hand, you have 4x3 finger segments plus the thumb to point them out. The actual issue is why we don't speak Esperanto, why the UK drives on the left, and the USA uses miles: network effects.
We also drive on the left in Australia. It was arbitrary which side to drive on since neither left nor right is superior. Miles vs km on the other hand...
It doesn't really matter which is superior or if there even is a superior option - the inertia of the existing system is large enough to prevent a change (The Swedish had a driving side switch at the very last moment it was feasible: https://en.wikipedia.org/wiki/Dagen_H ). If the imperial-to-metric switch is hard, how harder would it be to change a whole counting system that's embedded in much of the culture?