Why do humans look backwards to discover new things?

In short, it's laziness. Rather than figuring out how they should act, think, feel, and believe on their own, they would prefer to have others tell them how they should act, think, feel, and believe. And, rather than figure out whether the teachings are valid, or not, they would prefer to just look at the number of people who believe the teachings as a barometer of their validity. That, of course, is also foolishness.