It was supposedly to make shops more inviting to people from cultures that don’t commonly celebrate Christmas.
I find it hard to be doctrinaire or dogmatic. Even those who ask clerks to keep “Merry Christmas” greetings to people they are pretty sure will appreciate it, can still have very obvious Christmas displays and pipe carols over their PA systems. A little common sense will go a long way.
Cultures in America that don’t know Christmas is part of the larger American culture are extremely rare. I’d argue they’re non-existent. It’s like going to Germany and telling them to knock off the Christmas markets, there are Turks around.