If you actually measure the color of printed text, like in novels or newspapers, it is rarely pure black. It’s just really hard to make pure black in real life. It is typically a very dark purplish gray.

In addition, the paper it’s on is almost never pure white. And, as a reflective medium, the perceived colors of paper and ink vary with ambient lighting.

So in digital: should one create sufficient contrast to read? Yes, definitely do that. Stay well inside accessibility guidelines.

But a site absolutely does not need pure black text on white background to do that. And in fact at high screen brightness, that level of contrast risks creating little bits of ghost text in some people’s vision.