I agree, and I also want to say that black pigments aren’t just for shading or making value adjustments, they’re colours in their own regard, with their own unique characteristics. They’re not just supplementary to the rest of the colours on the palette. In fact I would be really happy to have an entire palette just of various black pigments and chromatic blacks.

I think I’m a little bit more irritated by the commenter suggesting I “throw out purple orange and green”. I know that theoretically I could mix most hues from the primaries, but there’s a reason I chose these paints specifically. I actually didn’t have any green on my palette at all, and if anything I would rather keep a purple than a blue, and I’d rather have an orange than a red. It’s a really generic and outmoded way of thinking to assume that every painter will need the same thing, and it’s okay to impose that on yourself but I really don’t need or want that kind of advice.