I agree that it's not "for no reason" even though the reason doesn't seem to be hunger or physical discomfort from needing a diaper change. There are other reasons for crying (many suggested here in responses) including digestive upset, allergies, reflux, contact, emotional distress.
Likely the parents are pretty stressed, wanting to stop his crying (which leads to relating to the baby as if there's a problem with his crying, as if he's doing something wrong, because not being able to help him/stop the crying creates a lot of discomfort for the parents.) That dynamic can ADD to his general stress & unhappiness.
Along with exploring other possibilities, you could suggest that the parents check out the book "The Aware Baby" by developmental psychologist Aletha Solter. It's about how babies cry either 1) for communication OR 2) in order to heal, and how to support them when they don't appear to be crying to communicate a need.
at 5:28 PM on Jul. 15, 2013