That is because the candy, and chips, and snack food, and fast-food, and soda industry are big bucks!
If they (the powers that be) can push the idea that it is your own fault then they have no responsibility and can keep racking in big bucks!
Imagine a factory was fluding the air with toxic chemicals. People were getting cancer... Not everyone, just some people... And it was getting to be more and more.... Soon a third of everyone was getting cancer from breathing the poison air.
But the company pushed the idea that cancer is a choice. So they can keep polluting.
And the crazy thing was people believed them. Even the sick people would hold their breath or wear a gass mask when out doors... and assume their cancer would go into remission on it's own.