The subject of mandatory easy modes ('story' or 'assisted' modes alternatively) being included in games has come up quite a bit recently, inflamed somewhat around the discussion of the (very challenging) Sekiro: Shadows Die Twice. Initially mulling it over while listening to the latest Bombcast, my first thought was to agree with Jeff's position that "sure, throw in an easy mode, nobody looses in that equation". It seemed like a no-brainier at the time. But thinking back specifically over my relationship with the Souls series, I really think those games would have been significantly harmed by having an option to alter the difficulty.
When I first played Demon's Souls way back when, I was very new to console gaming (PC only previously) and I was still struggling with just using a pad and analogue sticks, so that was a GREAT early choice. I made a bit of progress, and was absolutely beguiled with the game, but ultimately just couldn't keep up with it and ended up putting it down. I came back a year later with a much better grasp of pad controls and finished it, and from then on the souls series would become my favorite franchise.
Thing is, if there had been an easy mode I probably would have taken it when it hit that initial bump, and the experience I got from Demon's Souls would have been some shallow walk-through of a game with (famously) little narrative component. In a game that's fundamentally about learning and honing systems and technique I would have completely missed the point, and I probably would have fallen into the same hole when the later Souls games came around, if I even played them. I would have either missed out on, or destroyed the experience of what would be some of my most cherished games.
I don't think this argument applies to many games. Most can be enjoyed largely intact when playing through them on easy or 'narrative' mode, and I think it's good that so many include those now, especially narrative driven games (I've gotten a few non-gamers into the Uncharted series because they can wade through them like they're the terminator and just play the story, and it's great). But some, whether they are competitive, strongly gameplay driven, or specifically built around their challenge in order to be what they are, like Souls (or Super Meat Boy, Spelunky, and so on), would be rendered pointless experiences if the difficulty was altered beyond the authored intent. To the point that you'd get a better experience just watching a play-through - since then you would at least be vicariously exposed to the nuances that made the game special, through seeing how the player was handling it (and, you know, you could eat chips too).
//I have specifically neglected to go into discussion of 'accessibility' vs easy modes (i.e control options for those with disabilities), because it is a much broader issue than the nature of Souls games and their difficulty. By all means discuss that in another thread, but I fear that if it starts up here we'll all be on the prison bus to locksville penitentiary by the morning//