Mages don't understand the WHY or HOW of casting magic, they just mimic what to say because in their eyes the result is predetermined because that is how they are TAUGHT. Society idolizes and reveres a "goddess" that they feel is responsible for every single boon in their lives. Religious beliefs that ostracize twins(and most likely more) as subordinates of an "evil god" who were able to reach their hands far enough to injure their goddess. It's literally a world where the concept of independent thought(regarding anything that could upset the current society, such as the treatment of twins/effects of having twins around) is quashed by the reinforcement of a strict system of beliefs and condemnations designed to keep the common man ignorant.