Some things in life are so sad that there are no words to describe the amount of sadness, grief, and sorrow a person is feeling.
I assume this is why God allowed humans the simple act of crying.
When a person cries, they feel the sadness slowly ease out of them. They feel as though they are justifiably respecting a person that has died through showing their grief. They allow a moment of sorrow to overcome them and cry out a small portion of their unseen pain.