Because it's a disservice to the non-Jews who were gassed/baked/starved/burned/worked to death.
How, exactly, does giving a significant degree of attention to the Jewish victims of Nazism do a 'disservice' to the non-Jewish victims of Nazism? Is there only a finite amount of empathy and outrage in the world, or must it be rationed when Jews are the victims? Of course maybe you're just trolling.
Regardless of any more impassioned arguments, the Holocaust has to be seen as a central event of modern history because it brought to a (sudden, utterly violent and utterly complete) end a way of life that stretched back centuries and because it was the most extreme practical implementation of certain ideologies and theories that had become of central importance to the West during the previous century.
People only concentrate on the Jews when they talk about the Holocaust. Many people who were victims in the Holocaust were NOT Jews. They are not acknowledged, because people only concentrate on the Jews, as they had the largest numbers. This is denying the fact that JEWS WERE NOT THE ONLY GROUP OF PEOPLE TO BE IN THE HOLOCAUST.
