There's a comment at the end of the video, something along the lines of:

  Our old image of dinosaurs as ruthless killing machines 
  may be wrong, [...] some of them were caring parents, 
  with teenagers and younger offspring; they may have lived
  in herds; they could have been highly social.

That makes sense to me. There are evolutionary advantages to being social and sociability occurred in mammals in a relatively short time after the extinction of the dinosaurs. It would be pretty amazing if, in all the time the dinosaurs had, they never evolved to be social. Don't you think?