You can put people in an fMRI and you can't tell why people cry. Neuroscientists use fMRIs to get at things that are much more, to my mind, complicated and diffuse than crying. It's either the sad part of the brain or the sauerkraut parts of the brain to be determined by future scientists.
Is sobbing a survival tactic? What happened when Angela wept in front of her boss? And what do sauerkraut and sadness have in common?