How much of that is because they forced it to be relevant? It's one of the few obvious ways to separate people into groups, so they did that for their studies.

How much of that is because they forced it to be relevant? It's one of the few obvious ways to separate people into groups, so they did that for their studies. A popular categorization of humans before the mid 20th century was into three groups: "Caucasoid", "Mongoloid", and "Negroid". If that continued today, then there'd be tons of studies in the social sciences about how these three groups differ from one another, and it'd be therefore "very relevant" to a multitude of sciences. But we abandoned that false-trichotomy long enough ago that science does not miss it now that it's gone. It wasn't made relevant, so it's not. Of course the arrangement of my internal organs is relevant to doctors and medical sciences. As is my blood type and my cholesterol level. That doesn't mean you should be asking for my blood type when I'm registering for an online service (unless, of course, that service involves blood donation or something). That's the whole point -- it's really, genuinely, just not relevant to the vast majority of cases where it's asked.