From a recent NPD press release about Americans' changing eating habits over the past 30 years: "The average number of food items used per meal decreased from 4.44 in the 1980s to 3.5 in 2010."
Anyone who remembers supermarkets from the 1980s or before vs. the '90s, especially the mid-'90s, and later, will have observed an explosion in the choices available to the average American. There was no way that in 1985 you were going to find sun-dried tomatoes, olive oils from at least five different countries, or Thai green curry paste at the typical American supermarket. Now those things and so many more are commonplace. The only exceptions are food items for kids, as the '80s were the golden age for kids' culture in general. I walk through the breakfast cereal or candy aisles today and see probably 1/4 as many product lines as I would've seen when I was in elementary school.
The NPD story is that people value convenience and time-saving measures much more now than 30 years ago, as we're so much more over-burdened today. I wonder about that, though. Adults in the 1980s may not have been as crushed by boring or rat-race activities as they have been for the past 15 to 20 years, but that doesn't mean they were just sitting around with lots of idle time. Strange as it may seem in the era of helicopter parents, grown-ups used to have a busy social life of their own in the '80s and before. When new wave music exploded circa 1983, my mother went out to dance clubs every weekend, dragging my father along whenever she could budge him into dancing, and leaving me and my two younger brothers in the care of a now-vanished person called the babysitter.
So, a larger portion of adults' schedules may be taken up by stressing-out activities, but how much time they have to fix meals can't have changed that much. The shift toward convenience and therefore less variety in meal ingredients doesn't have to do with having less free time but with having so much more stress, which fixing a more elaborate meal would only compound. Back when adults were enjoying more carefree, though no less "full" schedules, adding another element or two to their dinner wasn't going to be the straw that broke the camel's back that night and send them on a postal rage the next day.
This shift is an extension of the trend over thousands of years whereby people who hunt and gather eat a far wider variety of foods than do people who are settled and have a cornucopia of items available for purchase through market exchanges.
The vast spectrum of choices at the supermarket is misleading when it comes to what a single person eats. Most of that diversity is due to variety between groups of people, and not at all to the variety that a single person in one of those groups eats. For example, if a supermarket has lots of animal products and lots of grain and plant products, you might conclude that the average consumer is an omnivore. But it could also be that there are two sub-groups of customers -- carnivores and vegans -- who have much less variety in their own diets than an omnivore does.
That's just what we see in today's super-stocked supermarket. There are a bunch of food tribes that have little variety in their own diets, but they all shop at the same supermarket. So there's the gluten-free area, the vegan area, the Hispanic area, the Mediterranean area, the frat boy 7-11 diet area, the TV dinner area, etc. Any individual who shops there has a very limited diet (one of the above), rather than have a diet that draws from all of those areas.
The same pattern shows up wherever hyper-mega-markets have replaced lots of smaller specialty stores. There's an incomprehensibly large number of choices of songs on iTunes, but the average music listener today takes in an extremely narrow "diet" of music. It's just that there are a billion different narrowly focused tribes, all of whom shop at iTunes. Same with the variety of books at Amazon and the more blinkered reading culture, or TV channels and programs and the more homogeneous range of shows that viewers watch these days.