Why is the front brake lever on the right if you 'drive' on the left and vice-versa?
I believe the reason is that the hand signals used to indicate braking generally involve using your 'road side' hand. In countries that drive on the left, this is your right hand and vice versa.

The back brake was considered the 'safer' brake to use during this pre-braking time when you're indicating that you will brake but haven't necessarily started braking yet.