the thing is, not everyone makes wise choices in their diet. you say you are whatever was closest to you, but I'm betting you still chose foods with some quality, at least most of the time.
I don't feel that it's necessary for everyone to always write down what they eat, but if someone comes and says they can't gain weight and their stats appear sub-par, they should at least write down their average diet for critique and pointers. often once they are pointed in the right direction they won't even need to write it down again. I don't mean to advocate that everyone keep a food diary every day (although I did for years), but rather advocate that they at least take a look at their diet to see if it needs to be tweaked before they decide that they just can't gain without steroids. I've seen a lot of guys that only count calories, then you break it down and they are eating lots of empty calories and way too many shakes. I believe we should point everyone in the right direction in hopes of helping them achieve their long-term gains. we some times get guys here who have good stats (and likely good genetics) who want to do their first cycle, and we don't preach diet because if they are 5'8", 220lbs and 10%bf they likely have a good diet already. we preach diet when the stats indicate they have a problem.