It could be for a more personal reason. Maybe he's going through some internal struggle or self - doubt, and wearing a mask is a way for him to create a new persona, a stronger and more confident version of himself. It's like a shield that allows him to face challenges he might not be able to as the regular Naruto.
He could wear a mask to protect his loved ones. If there's a new threat in the wizarding world that targets him and those close to him, a mask would be a way to keep his identity hidden so that his enemies can't use his friends and family against him.
Maybe it's to hide his identity or for some sort of protection.
Maybe it's for protection from something, like dust or germs.
It could be part of a plot device in fanfiction. The author might want to explore a different side of Naruto's character. By having him drop his mask, they can introduce new storylines, like how the other characters react to this new, more 'exposed' Naruto, and how it affects the overall dynamic in the Naruto - verse.
Maybe it's for a unique style or to stand out. It could be part of the character's design.
Bane wears a mask to control the pain and enhance his strength. It's a key part of his character's identity.
Perhaps the mask is just a fashion choice or it might be related to a specific story or event in the BT21 storyline that gives a reason for Mang to wear it.
One possible reason could be for disguise. Maybe he is on a secret mission and doesn't want to be recognized easily. In the Naruto world, there are many dangerous foes, and wearing a face mask can help him blend in or hide his identity from those who might be targeting him.
It could be part of a character - building exercise in the fanfiction. By putting Naruto in such an unusual and potentially embarrassing situation, the writer can explore how he reacts, grows, and adapts. For example, he might learn to be more confident in his own skin regardless of what he's wearing.
It would be really cool. He might look really intimidating with the hollow mask on. And his fighting style could change completely, incorporating some elements from the concept of hollow masks, like maybe some dark - energy - based attacks.