Arguably, they're more about the "typically not harmful" things than about the severe cases.
The severe cases are bad, but they're also obvious. Your ordinary management should be able to handle that. They often don't, and it helps to have a special level of appeal when the chain of management fails, but that's not the real reason for the job.
The real reason is that those "typically not harmful" cases are cumulatively harmful. They're bricks in the briefcase of every employee being discriminated against. They get all of the usual problems of life, plus a new set aimed at them. So they don't perform quite as well, and aren't the best when promotion time comes around. Then you end up with a whole chain of command who thinks that those "typically not harmful" cases aren't the reason everybody in authority looks like them -- and then do nothing about it.
Dealing with the explicit cases is easier, even though companies often fail at that, too. If they can't handle the easy cases, there's nobody looking out for the hard ones. And worse, people often say, "Look, we fired the blatantly racist guy, why are you still complaining that every single manager is white? It's just a coincidence, OK?"
I was thinking in general terms of bias and prejudice. You can’t remove it from existence because those aren’t qualitative terms. A decent person can recognize and actively combat bias, but not erase it. You’re still going to have some form of bias. At least I haven’t met a single persom who does not.
Now you’re talking about discrimination. Those can appear mild and harmless in single instances, but the accumulation is the problem as you said but also what we could call passive ignorance. In my experience people are often not even aware of being discriminatory, some are even well meaning, but are patronizing.
But there is a key difference in a spectrum of bias/prejudice and flat out not reflecting on our behavior.
I realize I‘m discussing semantics here, just wanted to explain how I understand those terms in my response.
I think positions like these are needed because there are severe forms of discrimination, hate, exclusion based on ethnicity, gender and so on.