Why is replenishment on the right side?

Why is replenishment always on the right side of the talent tree? For every class that replenishment is available to, it is always on the right side of their talent tree.

This is true for the Mage, Paladin, Priest, Warlock, and Hunter classes.

However, if we examine other important class elements, this is note the case.

Warriors have their tanking spec on the right side, like replenishment.
However, Paladins have their tanking spec in the center talent tree, as do druids.

Druids' healing tree is on the right, as is the Restoration tree for Shamans, but the Holy tree of Paladins is on the left (NOT the same side) and the Discipline and Holy trees for Priests occupies the left and center talent trees.

I could bore you with more examples, but the point here is well taken - replenishment is the only thing that is on the right side across the board.

I don't believe that this is fair, because some of us would prefer replenishment to be in other trees - so would it be possible for blizzard to expand replenishment to other talent specs and trees instead of forcing one of every 10 raiders to have a replenishment spec?

I await your response.