* Character development: Kurt's character is portrayed as a sensitive and introspective individual. His expressions, including the way he smiles and laughs, are often soft and understated. Hiding his teeth might contribute to this persona.
* Artistic choice: The show's creators may have chosen to have Kurt smile in a specific way for artistic reasons. Perhaps they felt it made him look more vulnerable or highlighted his dramatic side.
* Actor's preference: Chris Colfer, the actor who plays Kurt, might simply have a personal preference for a certain type of smile.
* Realism: It's worth noting that people often don't smile with their teeth showing in real life, especially when feeling shy or uncomfortable. This could be a reflection of Kurt's personality and experiences.
Ultimately, the reason behind Kurt's "toothless" smiles is likely a combination of these factors, and a conscious choice made by the show's creators and actors. It's an interesting detail that adds to the character's mystique and has sparked discussion among fans.