Perhaps that's the case for the current ruling class. However I'm pretty sure that most people would think of religion as "spiritual", and it served as a primary control mechanism from antiquity to the age of enlightenment. For that matter, the current brands of "spirituality" still serve as control mechanisms. They all have some framework that either controls by way of a religious hierarchy, or by encouraging self control within prescribed boundaries and/or practices.But Stoicism is nevertheless rather spiritual, so still sub-optimal as population control for the current ruling class.
So for those who think that some form of control is preferable to minding their own business, the question then becomes — which methods of control are preferable? Do we go with control based on superstition and a belief in the supernatural? Or do we prefer that those who want to order us around have verifiable reasons that make logical sense?
NOTE: Personally, I'm a non-religious quasi anarcho-pacifist. So I have a natural inborn aversion to any form of external control, and have no desire to control anyone else.