When is is time to turn off electronic devices

I went to my daughter's 8th grade ceremony last week.  It was a very nice event with lots of family and friends. It was a packed house.  I happened to glance to my left to see a sibling of one of the 8th graders with headphones on his head playing a game on a mini ipad.  Not once did he look up from the game to the events going onto the main floor.  The parents completely ignored the child...no effort made to correct his behavior.  After the event was over, we all moved as a heard out of the hot gym to the outside to meet the 8th graders.  I managed to land behind this young man still with his headphones plugged in playing the same game as he was walking out of the building.  I had to physically bite my tongue to stop myself from yanking those headphones off his head and asking him to pay attention to where he was walking.  Again, parents right there not correcting his behavior.  I was hot and irritated.  What is wrong with these kids and their parents?