I used to think that it was weird that the brakes were flipped (from a motorcycle point of view), but then I started to do a lot more climbing and realized that it does have its merits.

Most people are right handed, and descents are when you need the brakes the most, with the rear brake being much safer than the front brake. Your right hand is less likely to be fatigued than your left hand, so it makes sense to have that hand control the rear brake. While a lot of people say front brakes are more efficient, on flat ground it doesn't really matter since both brakes will be better than the front brake alone anyways, but on descents you don't have the option of using your front brake depending on the corner/steepness.