We tend to yield to temptation and have a lack of restraint when it comes to satisfying our taste palate. I think it starts with education and awareness. Its difficult especially when we are around people who are eating healthy as well. It makes it harder. For instance, think about making a fresh salad when you have ribs, steaks and red meat grilled and waiting. Its hard unless you start thinking outside the box.
Most people wait until they are diagnosed with high blood pressure, cholesterol or another condition associated with poor eating habits to start thinking a bit. Junk food and unhealthy foods come in many choices especially those processed boxed foods. There isn't as much selection or wow factor associated with fruits and vegetables. Also, there are many chemicals in junk food that make you crave the salt and MSG flavoring.
Great question. Hopefully, more people do change as many of the conditions that come from poor eating are life long. Its better than taking medication for life; because you cannot forego your poor eating habits. Its the cost of indulgence. And it is costly especially being admitted to the hospital.