When you have killed a skeleton and want to bury it back in the ground.
Corpses in Skyrim can be an awkward thing. Some of them stay around for while others disappear. You can use the fast-travel-and–wait trick but it isn’t very polite. The most difficult death ritual is ‘waiting for the body from the worldstate’. It’s not one of many. Which is perhaps why someone has made a Pay Your Respects for Skyrim, to let you bury and say goodbye to the fallen.
You can create a grave to honor your friend or murder victim when you bury them. It will include their name, date and engraving. The mod description states that you have the option to choose from a pre-made engraving or to create your own. I’m sure that I’m not alone in thinking about those joke tombstones.