They don't.
But when your entire people has been singled out for extermination, it kind of gets your attention. Especially considering that the effort met with considerable success.
It is not that it is ignored or unknown. In my Jewish Sunday School textbook, from 1970, it stated that revised estimates showed 5.4 million Jews died in Nazi extermination operations, as well as about six million non-Jews.
Germany in the late 1930's established racial purity laws and administration to ban Jews from daily life and sight. The death operations and concentration camps were set up to rid Germany and conquered areas of Jews and other "troublemakers".
We regret the loss of all innocent life. Losing almost half of all Jews on earth in five years is so horrible to contemplate - the worst tragedy in our history. It is, I guess, for other (non-Jewish) scholars to provide more information about the other unfornutates who perished in the fields, woods and camps. One posible problem in the past was that most of the people killed came from areas that soon came under Communist control. Deaths of Christian activists or leaders would not have been in the Reds' best interest to highlight.
I can't remember if they made a point of noting non-Jewish victims of the Holocaust back in Jewish day school (it's been a long time), but I'm pretty sure they taught us that stuff. Holocaust education is an important part of Jewish culture, they try to do a thorough job of it.