I think the public displays are a result of the people’s really being bored with each other and with physical interaction in general. Nowadays, young people see it all over from early childhood, they’re constantly told that there’s nothing more important or interesting in life ... and then they find that it’s really pretty much a drag, especially if you’re involved with immature and self-centered partners (as how could you not be, given their age and culture?).
So the only thing that’s the least exciting is making a scene in public (or on Youtube, etc.). It’s all about getting a reaction from observers.
In the case at my son’s Homecoming Dance... I think it was a way to get a reaction. From my understanding, the “couple” found it amusing that another kid threw up. I am glad that I have taught/still teaching my children that hand holding is fine, a smooch is okay... anything past that is private and not for public viewing. Decorum...