Something I haven’t seen other commenters bring up that can have a huge impact, is the overall lifestyles people are living.
The unhealthiest years of my life were when I was working 2 jobs and struggling to keep a roof over mine and my 3 kids heads. Stress and depression were huge problems and money was tight, so sometimes the little bit of dopamine or serotonin from eating a “treat” were the highlights of the day. Add to that, the guilt of not being around to cook regular meals for my kids lead to 1) making large amounts of food on my one day off that could be eaten as leftovers throughout the week or 2) easy convenience foods (frozen pizzas, boxed Mac and cheese, etc) that the kids could make when I wasn’t around.
Fast forward many years - my kids are adults taking care of themselves and I’m down to 1 good job that offers financial stability. My diet and health have completely changed. I actually have the time and energy to cook and plan better.
I’m not saying this to shift blame or responsibility, but to bring a different experience. When I hear (hopefully well meaning) people suggest “just cook healthier meals” it strikes me about the same as “stop eating avocado toast and you could afford a house.”