Listen to people talk about a coworker or boss who left their job. It sounds like they died. We talk about how things used to be when they were still here. We say that things will never be the same again. We wish that they were here just a little bit longer (unless we hated them, in which case we have never been happier to see them go).
But it's more than just what we say. Our actions change, too. We go through the same stages of mourning and coping that we do when somebody actually dies.
Non-lethal loss is a relatively untapped pool of potential. It does take some skill to have the audience experience the character's sense of loss, even though nobody died, but it is hardly an impossible feat. And once you can do that, you can bring in more nuanced feelings. We can explore the human condition without going to extremes or cliches, and that in turn allows for more nuanced events to happen. For example, we generally can't bring people back from the dead, but you can visit your retired former boss.
The other interesting aspect of non-lethal loss is that it does help prepare a person for lethal loss. Death is always a tragedy when it happens to someone you care about, but having experienced tragedy in general, and having experienced loss, it gives you points of reference, shows you how you have coped before, and how you have survived those feelings.
This again adds to the potential nuance to a story. By having a character experience non-lethal loss, and learn and grow from the experience, it makes the experience of death a relatively new one by having different shades in the character's eye.