There is more to the game than just challenge, but that's the thing: it's a core aspect that strengthens the game on a whole. Sense of satisfaction from conquering a challenge, a thrill in pushing forward and seeing new areas while being weary about new threats, or coming back when you're much stronger and trouncing the shit out of everything. You'd get some of it with a nerfed difficulty, but not fully, and if they have to compromise multiplayer for it then it's screwing over everyone potentially.
That was an... unfortunate analogy above, but a better one would probably be like pursuing a hobby or working out (albeit not AS rewarding, yet much less time consuming normally). You work at it, push yourself, get better, and receive a sense of satisfaction from accomplishing new goals. What it sounds like he wants is more like... well, like reading a book or watching a TV show/movie, which for some games IS fine, even an arguable fault if they fail to include easier difficulties who just want to enjoy the narrative (ME3 giving an option to let choices be made automatically bugged me FAR more than "Narrative difficulty", it's actually a similar problem as to this Dark Souls argument here albeit in reverse), but Dark Souls isn't really one of those games. You'd probably get the same enjoyment out of story just by reading a ripped compilation of item descriptions and watching Youtube videos compiling all of the dialogue.
I don't think it's really TOO hard if you just want to do a single playthrough to see things: play carefully, check tips online, and summon plenty of help for the boss battles. It's in NG+ when it can potentially reach the point of being too damn infuriating, and if all you wanted to do was get through and beat the game then there's not much point to being upset, start a new character or do something else at that point.