They still do in a way. Just a way to try and reach the holes left in the survivors hearts.
That's a good question. There are probably various answers for different cultures. I would think that the answer starts with the simple fact that these goods, and items, were simply the possessions of the deceased, and remain their possessions even after death. And so are likewise buried. Western cultures don't think that way. We want to disperse possessions among the living after a death - even look to profit from it.
Grave goods accompany burials for a number of reasons. The most typical reason given is that grave goods represent a belief in an afterlife by the culture that buried the individual and that the grave goods are intended to be used by the deceased in that afterlife.
They may also serve as offerings to deities on behalf of the deceased.
Grave goods may also be the possessions of the deceased which may have been regarded as ritually unclean by the living because of their close association with the deceased. By placing in the grave, it would prevent the spirit of the dead from "haunting" the living in search of their belongings.
In the modern Western world, people are often buried with a few belongings - jewelry, stuffed animals or toys in the case of children, favorite items of clothing, etc., more as an acknowledgment of the hobbies or favorite items of the person.