People eat three meals a day, for their entire life, it's one of the subjects that is most obviously worthy of study. Yet we are finding out that we didn't know some pretty basic information about this field, or otherwise that information was inaccessible until recently. People who questioned whether or not fat might be good for you have been ridiculed by professionals my whole life. In an area that is an obvious choice for study, an area that might by vital to human progress, we know very little because of how little actual research has been done.
I don't believe in a lot of things that are commonly accepted. Frankly, I don't have time to do my own research on a lot of it, so I reason from principles, and from what I know to be true about the world. We can't be experts in everything, we don't have the time, so we rely on others. As society has progressed, there is an ever greater number of fields we cannot be an expert in, and so if the experts choose to they can successfully lie. We don't live in some super altruistic society where people have no reason to be dishonest.
When they told you Santa doesn't exist, you should never have stopped questioning. If your parents would lie to you about Santa, why wouldn't the government or other segments of society lie and give you fairytales about any number of other topics?