In the present day Cutie Marks are readily understood by most, a filly’s development is common knowledge.

Unfortunately +1000 years ago things were different, there was a harsh stigma for not having a Cutie Mark after a certain age and was a sign of inferiority.

Ponies without Cutie Marks would go to great lengths to cover their flanks so as not to bring shame to themselves and their loved ones.

This is particularly humiliating for the Equestrian Royal Family after Luna became overdue for her Cutie Mark, Luna was confined in her room in attempt to hide her from the King and Queen’s subjects.

However when Princess Celestia began raising the Sun AND the Moon, the moon being Luna’s purpose, the King became enraged. Luna was banished, being banished was extremely traumatizing for little Woona, one can only imagine what trauma would occur if she were to be banished again.

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Dialogue between Celestia and her father after Luna is banished

__Father:_ “Come to dinner my one and only daughter.”_

__Celestia:_ “What will become of Luna?”_

__Father:_ “Luna shall be alright, we began denying her supper the day she became too old to be a blank flank. I have banished her to a place where she can better understand her assigned task in life.”_