Most people have no clue what constitutes a healthy meal. Moreover, they are strongly incentivised to eat crap by the fact that crap food is (much) cheaper than healthy food. Combine the two, and you have vast numbers of people who basically eat sausage rolls, pizzas, burgers, chips and chinese takeaways (probably not the worst of the bunch), along with epic-size sugary sodas and mega-calorie coffees on a pretty much daily basis.