The Ballad of Songbirds and Snakes question

I had the same thought. Essentially, the entire film revolved around their love for one another. Why, then, didn't they add the kiss? Personally, I believe it was done to add "suspense" to their romance. It was fitting that they would kiss each other goodbye in the novel because they had already been through so much together with all the deaths between the district and capital kids as well as the fact that Coriolanus would visit Lucy Grey on multiple occasions at the zoo not just twice as we've seen in the movie. (it still doesn't make sense to me why they kissed but whatever). In any case, some of those more intense scenes were cut out of the film, so, it probably wouldn't have made sense for him to kiss Lucy Grey as he was saying farewell. There was just not enough plot to portray them as lovers just yet.