Fiction writers whitewash characters when, for example, they base a character on a person whose real name is Rosenstein, but they rename him Stone and erase anything Jewish about him or his family.
I would bet you meet many more Johnsons, Smiths, Thompsons, Robertses, Millers and Joneses in fiction than in real life. Authors do this "ethnic cleansing" hoping to "universalize" the characters or create a "blank slate" supposedly without ethnic or historical baggage. Screenwriters, actors, even toymakers do this too. Mattel's Barbie doll, Barbie Millicent Roberts, dumped her boyfriend Ken Carson for Blaine Gordon. Midge Hadley Sherwood was Barbie's best friend and Francie Fairchild her cousin. Barbie's darker-skinned friends, such as Christie, an African-American, have no surnames. It was a business decision to tiptoe around the issue. All "ethnic" names come with "baggage," it seems. Can't name her Christie Jefferson, or Christie Afolayan or Christie Muhammad. All loaded with baggage! Better no surname at all.
Paging through the short fiction in a recent literary magazine, all of it "realistic" and set in the U.S.A., I found characters named Freeman and Mr. Henry. All the other characters, perhaps 30 in all, had first names only. Yet in reality your surname rules your life. Why such a dearth of surnames? Tension around this issue -- do ethnic names trigger reader prejudice? Do non-Anglo names distract the reader?-- makes it simpler for creators to default to Anglo in name and in being -- or, simplest, to default to no surname at all. This is in tandem with the tendency not to describe or name the story's setting, thinking that's more "universal." (Editors call this "hoboes in space.") As fiction writers gain experience they do this less and less.
Anglo surnames for your characters are not universal or neutral. Simply be aware of that when naming characters. At one time we opened the phone book at random to break ourselves of the "Johnson" and "Thompson" impulse. Today, seek out the surnames of the football-team lineup at the college nearest you. Because of migration and immigration, legal or not, nearly every nation is a nation of immigrants. Is it too much trouble to imagine what traces of Germany might be left in a character who is a fourth-generation American named Hochmuller? And no fair substituting Irish or Scottish names. Not everybody is from the U.K.!