OP, guess what. I second you. Straight and simple. I also second poster #3 I believe. There is a genuine display of emotions and "manufactured" one. Sometimes genuine piggy backs manufactured, sometimes the other way around. Either way a crowd instinct kicks in. Also, as this "cliche" is mass promoted by media, it becomes a "good tone" to participate. Jimmy, YOU are not grieving with US? And what can poor Jimmy do....
I also believe that genuine feelings lack desire for public display.
Op, I bet a safe buck thise will annoy you too:
Fake Smiles Are Bad for You & Here