In short, it comes down to a learned pattern of thinking and behavior where you assume that others have authority, expect them to abuse it, and try to protect yourself by knowing your place.

Exactly this^. A power imbalance or heirarchy is not inherent in therapy (though a therapy situation may be used as a vehicle for abusive action by an unethical practitioner), but rather a projection that the client does or doesn't bring to the situation. And like all learned behaviors, it can be changed.