Many people eat junk food because it tastes so good. Everyone knows it’s unhealthy for them to eat it but junk food was made to stimulate your taste buds and makes you want more. Even though junk food has no nutritional value it’s mostly just for the taste and they don’t want to cook.
So I think the main reason people eat so much junk food is because it opens your appetite making you want more. People eat junk food, well, because it tastes so darn good. We're hooked on the pleasure of eating rich, sweet, and salty foods that look, smell, and taste divine and delight all of our senses. The food industry creates products with this in mind. We consume these products, which alter our metabolism and train our taste buds to desire them, and the food industry further fuels demand for them through alluring advertising.
And I think most people understand the fundamentals of a healthy diet, which includes plenty of vegetables, fruit, fish, chicken and some lean meat. Unfortunately, many people who need to improve their diets continue to eat junk food, or food high in simple carbohydrates, preservatives, fat and salt, even though they know it is most likely harming their health.