Well, one possibility could be that it's a moment of deep friendship. Naruto might kiss Sakura's forehead as a way to comfort her after a difficult battle or a personal loss. It could signify his growth from the goofy kid to a more mature and caring friend.
It could symbolize protection. Naruto is a strong character, and by kissing Sakura's forehead, he's sort of pledging to keep her safe. It's like a knight protecting his lady in a way, but in the Naruto universe context.
The kissing scenes in such fanfics depend on the tone of the story. If it's a romantic - comedy type of fanfic, the kiss might be a bit clumsy or unexpected at first. But if it's a more serious, angsty fanfic, the kiss could be a desperate or longing - filled moment between Sakura and her new partner.
One reason could be that it's unprofessional behavior in a school setting which is mainly for learning. Schools are places where students should focus on academic and social development in a proper way.
There were kissing scenes in " Celebrating Years." One of the more famous kissing scenes was Fan Xian and Lin Wan 'er kissing in the rape field. The kissing scene sparked widespread discussion in the film. Some viewers thought that the kissing scene was too intense, while others thought that the kissing scene was necessary for the development of the plot.
Students can focus on other appropriate forms of social interaction like group discussions, sports, or club activities. This way, their attention is diverted from any behavior that is against the rule.
The Kissing Booth is based on a fanfic. It's not a completely original concept. The fanfic's popularity might have led to its transformation into a more mainstream form of entertainment.
I recommend "The Story of the Hero of Haruno Sakura in the Wood Leaf." The main character is Haruno Sakura. Without a system or a cheat, he can only rely on his own fists to fight for the world. Watch me use this pair of iron fists! I hope you like this fairy's recommendation. Muah ~π