Just because something is common and widespread doesn't mean it should continue to be common and widespread, though it will continue to happen due to human nature. And yet, people striving to be constructive and positive won't celebrate the death of a stranger. "Do unto others as you would have them do unto you" is a cultural lodestar found globally for a very good reason: cheering the death of others may lead to others hoping to cheer your death, and that potential is enough to significantly curtail offers of constructive and positive assistance from the victims to the perpetrators, leading to a gradual social degradation within the perpetrators. Certainly remember and even memorialize a person's death, but the exaltation of a person's death is a sure path to cultural collapse.

Now, that's assuming people are one unified group. In reality, most people are forced into an "in" group or an "out" group. The "in" group exalts the death of the "out" group member, so the "out" group members must respond in kind. That eventually leads to the degradation of both groups, leaving the "above" and "beyond" groups with the remnants. In turn, the destructive and negative conflict continues.