It doesn't depend on a belief in the afterlife. What archaeologists call "ritual" need have nothing to do with religion. Washing your car and mowing the lawn are American suburban rituals. Halloween, Christmas, and birthday celebrations are ritual. We also have ribbon-cuttings and graduations. When I was growing up we "pledged allegiance" to the US flag.
You don't have to understand why you are doing something - or even that you are doing it at all - as long as it works and gives you a benefit, however small. Without proper understanding you will also have false positives, but it's better to be assume there is danger than to assume there isn't any. False positives outweigh false negatives. (To a certain level, of course, too much of it and paranoia becomes harmful again.)
[1] https://en.wikipedia.org/wiki/Necrophoresis
[2] https://www.npr.org/sections/krulwich/2009/04/01/102601823/h...
Also, there could be many such reasons for burying/burning someone dead with his/her possessions. My point was that almost always it becomes "elaborate rituals and beliefs of afterlife with same worldly possessions that they had here on earth" - just because we know pharaohs/ancient Egyptians did it.