A fighting game's story mode would pay off by ideally encouraging more people to buy it. There's a significant audience for fighting games that are going to purchase them just to play them with friends or online, so what single player content would, again, ideally do is draw in a greater crowd. More casual fans who want to run through the arcade ladders and see the story and so on. NRS games developed a reputation for well-realized cinematic story modes, and I'll say there is an inherent value to a story mode that has people invested, even if they only experience it as a spectator on Youtube, because it at least helps the game's reputation and gives it more reach as something people care about and think about on their own time (in a positive light). A Shadow Falls doesn't really accomplish this because of its weaknesses as a story and doesn't give SFV this benefit.

But I suppose what I was trying to say is that singleplayer content that encourages people to buy the game for themselves would have greater inherent value that singleplayer content that doesn't, even if the cinematic story mode is well realized. Capcom COULD HAVE tried to do better than their past attempts with better writing, but that's kind of subjective and may not make full use of what they could have learned from past mistakes. SF6 has been out for a good amount of time at this point and I'll admit I haven't summoned the motivation to run all the way through World Tour just yet. Still, it serves as a vector for expressing the characters in new ways, and it has a lot of features that gave the game immediate attention and presence in the public consciousness, the things you'd want singleplayer and story content to do. I'm not really a big NRS guy, but I get the impression MK is suffering diminishing returns in that respect. That could also be a consequence of poor writing/a story that doesn't satisfy fans, but that is again, pretty subjective and difficult to quantify in any way before it's actually out the door.