The simplest answer to the question is simply: Because it works.
When we talk to a therapist in a fully alert and conscious state, we may be able to reason and analyze in ways that are important for understanding the implications of what we do.
But even when we do understand, change rarely comes easy.
We cannot change, because, on some level, we are addicted.
We are addicted to the same patterns, the same neurochemicals, the same behaviors. Hindus call this addiction “karma.” The Gnostics called it “sin.”
Any way you look at it, knowledge alone does not bring freedom.
Why is this the case?
Because our addictions are based on our experiences. At some point in our past we experienced something that was so intense that we bottled up the experience and brought it inside of ourselves. We allowed this experience to become foundational for all of our future emotional responses.
This is the karmic “drop” that resides insides of us, ready to be awakened at any moment to cause us to react. For Sigmund Freud, this entailed a drive to endlessly repeat the events and responses that are most traumatic to us. At some points in his writing he refers to it as the “Death Drive.”
In order to counter an experience one needs to have another experience in return.
It is not enough to reason in the state of consciousness in which we file papers or discuss the news.
Hypnosis allows us to revisit the sources of our addictions in a state of emotional intensity. With all of our senses engaged, it becomes possible for our new experience (the desire for freedom) to override the old.
Often hypnosis brings transformation in a single session.