It's a continuum of sorts. I don't actually believe it's that hard nutritionally to get big and strong provided you'll actually eat. Those in the strength and iron game tend to eat more protein and "cleaner" foods anyway, i.e. single ingredient foods, and pack away some serious calories. Provided the training is correctly programmed and implemented and the sole goal is strength/power, I'm not sure a specific nutrition protocol is warranted outside of the commonly given advice "eat big" until one starts to get competitive and/or recovery starts to be an issue.
That being said, I see far too many people fail trying to get strong, big, jacked, etc. because they won't eat the right stuff. They won't eat enough protein, carbs, and/or fats to recover properly and they can't accurately describe what they're eating when it comes time to address recovery-related stuff so simply saying "eat more" might not be good enough advice. For example, if someone is already eating more than enough protein and fat but is inadvertently skimping out on carbs for whatever reason and is noticing their recovery is going to hell, well they need to know that they're actually only eating 100g of carbs a day and that is likely the culprit. The advice "eat more" may, in fact, cause them to consume more carbs, but then again the person might just eat more protein and fat, which may or may not work.
When it comes to higher level competitors with people of average or less than average genetic endowment, nutrition starts to paint a much bigger picture, especially if there is a distinct advantage to being a lighter, yet stronger competitor (weight class sports, cycling, running, etc.). Simply put, there's no black or white to this issue, just a whole lot of gray, which is further compounded by the fact that people do all sorts of silly things dietarily and royally screw themselves up metabolically. Finally, since it seems like a lot of people start or continue to train because they want to achieve certain goals, be they aesthetic or performance related or both, they tend to require at least a modicum of dietary accountability to eliminate one of the variables with a great potential of increasing or preventing results. This goes doubly so for people who are well past the novice phase and/or want both performance gains with an eye towards aesthetics.
I think you'd be surprised at just how many people take their nutrition seriously, whether they admit it or not.