With regards to Dark Souls, and it's not something I've ever played myself, but it seems to cash in on the exclusivity and prestige of managing to beat it, allowing the committed player to seperate themselves from those who don't "get it", and potentially trick themselves into thinking it's good. Maybe that plus the sense of accomplishment being heightened because you've been denied it over and over, like successfully performing a difficult skateboard trick. Because it's ridiculously hard, it's good. But then some people love it for the game world, which is a different thing altogether.
I remember playing Rick Dangerous for hours when I was a child. And losing my last life time and time again on the same level after hour to reach that level again. I hate difficulties, and platformer, and perfectly timed jump and strike. But there is something weirdly satisfying in a game that keep beating you down. I never played Dark Soul, and wont enjoy it. But I get the appeal.
I do too, but only if it's fair, and that's the difference. I don't mind a hard game that doesn't dick you around. I'm playing Dead Cells right now, which is clearly influenced by Dark Souls, but I'm loving it despite dying almost as fast and definitely as often. Because in Dead Cells, I never wonder why I died, and it's never due to RNG bullshit or opaque mechanics. Meanwhile, I can already feel myself getting better, to the point that I'm flying around the first level dodge-rolling and slicing things to bits like a buzz saw, and it's a blast. Dark Souls made me want to invent a way to kick a game in the nuts.