In the startup I worked for, the HR lead was the CEO's significant other. They had made fundamental contributions to the operations of the company since its inception and relatively humble beginnings. Once it had grown beyond a certain size, there wasn't really any particular executive position within a logical company structure for them to fill. The individual departments were run by people more qualified in those areas. I think it made sense for the company to continuously recognize their contributions (and obviously the boss isn't going to fire their partner), but HR ended up being mostly just a cushy job for them to fall into.

It was one of those companies that likes to say its "like a family", but really there's an in-crowd (i.e. the founding staff) and everyone else. I was part of the former, so I could be honest and open with them with regard to HR issues and be supported, and that was nice. But on the other hand, I witnessed HR actions related to incidents involving other staff that caused me cognitive dissonance, because it would've been handled differently if I were the staff member involved. More than anything else, because I had found myself in the right place at the right time. Because I was a part of the landed gentry, as it were. That's fucking bullshit, and the experience made me realize that they weren't actually different from other companies like I had thought.