Do we have obligations to the dead and why?
The idea of an obligation towards the deceased is a cultural construct. Some cultures see death as a transition between lives, where individuals must continue their relationships with the living or risk being condemned to suffer in the afterlife.

In these cultures it can be seen that fulfilling obligations to the dead would ensure that the soul will find rest peacefully. However other cultures do not believe in an afterlife and so there are no such expectations placed on the living.