Why The Baked In 25% Increase To GCD For Single Click Rotations ?

Honest question here, why is there a baked in 25% increase to the GCD for single click rotations?

Classes are constantly being changed, pruned, rebalanced and updated, and it seems to me that adding an obligatory 25% increase to the GCD is overly punitive to the player base.

Couple these ever changing classes with new and cutting edge encounter mechanics, it feels like an unnecessary penalty and generally counter productive to the expanding access to the end game content for the player base.

Your thoughts ?