Why does petting a dog make us feel better? It's not just because they're cute, they can also bring us comfort. The human-canine bond goes back thousands of years. Dogs descend from wolves and have been attracted to humans ever since we began living in settlements - a source of tasty garbage. That created an advantage for wolves to live near humans, and since it tended to be the less aggressive wolves that could do this more effectively, they essentially self-domesticated over time.
To some, the idea of sending a dog to a grieving person might seem too simplistic. But that very simplicity is part of what makes the connection between humans and canines so powerful. Dogs have excellent listening skills, and they demonstrate unconditional love. They don't judge you or talk back.