Steve Jobs had a bug up his butt about machines that could play games being "toys for kids" and he did everything he could to have the Mac treated like a "serio

Steve Jobs had a bug up his butt about machines that could play games being "toys for kids" and he did everything he could to have the Mac treated like a "serious business" machine, part of that included sticking with boring corporate monochrome graphics. I think he was mostly trying to avoid comparisons to the 8 bit Apples. The other reason being of course that VRAM was breathtakingly expensive at the time and you could save some money by going with 1 bit per pixel. All in all the Mac with its 512x342 monochrome display tended to come out looking nicer than the contemporary 320x200 16 color EGA graphics.