cooking 101 really should be a mandatory course in high school.
realistically a lot of americans just have awful dietary habits. my mom cooks but much of the time it's processed stuff or things you'd find on the recipes section of Pillsbury's website. when I worked at wendy's my manager told me her husband doesn't like the taste of water and subsists entirely on Barq's root beer. the amount of soda americans drink on a daily basis is just ridiculous. you literally cannot go to a walmart without seeing at least one ham planet scooting around in their motorized cart which is almost always full of chips, snack cakes and sodas.
it's a generational thing, a lot of people grow up in households where these horrible dietary habits are treated as normal and so they don't seek out anything else. that's why fad diets have been so popular, the concept of altering your overall nutritional intake as a lifestyle adjustment is too extreme for most people to handle or even consider.