Humans have a problem with those sort of issues. Furthermore when surrounded by pretty much everything sugar, its kind of hard to avoid. Imagine if we were to find out tomorrow that people who use facebook are 60% likely to die of a seizure caused directly by facebook within the next 50 years. And we find out by a vague hard to prove no direct correlation study. Would be pretty hard to convince everyone you know to stop using facebook. What if it's too late? Etc.