As we learnt at home or at school, mixing yellow and blue makes green; we didn't get taught much about black, however. Mixing all the colours produced a very dark brown: that was all we knew.
But on a screen we assume that lights-out is black. Practical businesses that are wanting to produce something to look at and read will not be interested in esoteric theories or arguing about colors being true, except inasmuch as they might do an impromptu survey if something looks wrong to them.
The selection of the primary colors for printing is done by taking the primary colors of light, and finding their complement; were pigments and the process of mixing them perfect, these secondary colors would produce black.
Of course, anyone with a decent encyclopedia knows all this.