I'm not sure what country you live in, but from a relative of mine who works in a cancer treatment centre, there are a fairly large number of patients who eschew treatment in favor of herbal remedies for instance. They eventually get treatment when said remedies don't work but the cancer would have gotten worse by then. It's partly false beliefs, wishful thinking or just avoidance of the issue. Do very many people really believe that a herbal treatment is going to cure cancer and the whole medical community is stupid? No, but for many people it gives them enough to pretend that everything is going to be okay and they don't have to worry.