I know a lot of Christians don't believe in demons, despite the fact Christ said to send them out (inherently acknowledging their existence.) So, this question may be inappropriate for those who don't believe in demons, possession, principalities and archons.
For those that do, do we realize how terrifyingly hard it is - how terrifyingly dangerous it is - to cast out a spirit from a body? Do we understand that people die trying to perform exorcisms, or become possessed themselves? Do we realize spiritual entities are intelligent enough to drive the possessed body into convulsions, foaming and other "obvious" possession signs - that someone could be deceptively possessed?
It isn't like the movies, and The Exorcist is about as close as it gets (but, is still grossly underexaggerated.)
Demons have been wandering spirits for thousands of years. They know humans. They know subtlety. They learn. It isn't like taking out cancer; demons are highly intelligent entities with knowledge of this world, and the other world. It isn't child''s business.
You can't teach exorcisms, because you can't teach faith. Sure, you can ward your areas, and stock your hips with crucifixes, silver, iron, and holy water. But, if you have no faith, or if you have less faith than the threshold needed to contain and control these entities, you put yourself and everyone else in danger.
Often times, exorcisms aren't actual removals, as these entities attach themselves to physical objects to tether to the physical world - with the hope of possession again. In addition, telling people to move doesn't do anything when dealing with spirits - unless you know the ward to contain the spirits.
This knowledge can be taught, but the execution and power thereof CANNOT.