Thanks for your feedback. I'm not trying to be snarky, I'm really not.
I do know a lot about the eating habits of people as I ask them that (and about all of their medical issues) in my line of work. I'm not with them 24/7 but I am given their medical records and I spend a great deal of time working with them on their family and health issues. So I have more access than most people do, including food diaries.
A lot of times people have to feed their children what they can because of their economic situation. I get that and I know a lot of people in that situation. That's not who I am talking about. Rather then going back and forth where you find every exception, I'm just going to say I'm talking about families with enough money, time to cook, whose kids don't have sensory/developmental issues. Do you really not know anyone like this who breastfed but then gave their kids Coke, Lunchables, Wonderbread, Kool-Aid, Snickers, blue yougurt, etc, sometimes even simultaneous to nursing?
Rather than arguing what life was like 100 years ago, I'll say I didn't have to pick 100 years ago. I was just selecting a time and place where we didn't have swirly yogurt or whatever. I could have said 1000 years ago, Bombay in the 1940s, rural Tanzania 20 years ago. There's no magic about 100 years ago. Pick any time and place where these processed foods were not available. It's still a valid question.
And I'm not just talking about American or western European cities. Your examples have been the research you did wrt American socio-economic patterns and the foods of American cities 100 years ago (yikes on the crisco sandwiches). People in other countries 100 years ago (or 1000 or whatever) also didn't have access to these foods that are the "only foods" some kids will eat. (I say this again with all required disclaimers about the family economic and health situations.)
I'm not hiding behind a question in order to not trash food choices directly. I'll ask: "Why would someone feed their children that fake crap if they don't have to?" Is that better? Does the "if they don't have to" correctly place the question in the realm of people who feed their kids this food for no good reason? Do you think it's possible these people I'm talking about exist? I think formula is necessary in some cases (and I'm sure people would be happy to spell out all the examples of why they needed formula, as I had to as well), but that doesn't mean nobody is giving formula for convenience or whatever. I'm talking about the solid food equivalent.
Like many kids, when I was growing up I spent a great deal of time with my girlfriends, sleeping over, going in and out of each others' houses, etc. I was intimately familair with their family's habits (and obsession with Shawn Cassidy!) and I am certain that they didn't have health or developmental issues and they had enough money and the mamas stayed home. At my best friend's house, why in the world were we given Coco Puffs everyday? I was too young to grasp so I didn't ask but looking back I think it was because it was convenient. We would sometimes ask for eggs, toast, etc. but were handed a box of Coco Puffs and (chocolate!) milk instead. I don't judge those mamas because I am certain I am doing something ridiculous in raising my child.
But that doesn't make what happened any less ridiculous.