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.
A 'kissing fanfic' is a type of fan - created fiction that focuses on romantic or passionate kissing scenes between characters. It often involves characters from a particular fandom, like characters from a movie, TV show, or book. Writers of kissing fanfics usually explore the romantic relationships and the emotions associated with the act of kissing in their stories.
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.
Well, without having read the novel, it might also explore themes of growing up. Kissing games could be a part of the characters' exploration of their budding feelings and attractions, so themes related to adolescence and young love could be present.
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.
Since I'm not familiar with this novel, you could try looking for reviews or summaries of the book online. Maybe they will mention any interesting kissing games in it.