If they were asking about demon/dark souls, they were likely not extremely casual. The casual fans I know play Minecraft/Madden/phone games and have no idea what Souls is
Also, you gotta be deep in the Souls bubble to just assume everyone loves that series
Maybe casual isn't the right word. We're talking people who would pick up and play a couple games a year, but were pretty much sticking to madden/halo/mass effect.
They were asking because I was playing them at the time. It was an easy sell though because they were usually playing most games together in college.
On a separate note; I don't think that difficulty is the only draw for these games. They have a lot of detail, great atmosphere, and are able to portray a story without saying much of anything.
With that said though, I can very very easily see why anyone might dislike the games completely. Different strokes.
Football related: Anyone see the picture of Adrian Peterson in a sultan outfit riding an elephant on his birthday? We'll take a 2nd for him!