People are driven by two survival instincts. The drive to conform and the drive to rebel. From an evolutionary perspective, this creates an interesting conflict. Conformity is a very useful trait if you are potential prey. Herd animals, in larger herds, can afford to, and do, put less effort into watching out for predators than than do animals grazing in smaller groups. The reason they can afford to do this is because they conform. If suddenly the deer next to you starts sprinting, you don't need to see the attacking predator for yourself. You don't even need to verify for yourself which direction its coming from. You just conform. You run with the rest of the gang. The one or two rebel deer, who refuse to panic just because everyone else is doing it, but insist on seeing the mountain lion for themselves before they run quickly get Darwined out. Conformity saves lives.
But conflicting with that primeval instinctual programming, human beings have another instinct. The instinct to rebel. We are one of the few creatures who have had some success getting out of the box. All our really cool advances in technology, agriculture, etc began with one or two or more individuals not doing what every one else is doing. All our heros are innovators, outside of the box thinkers, trend setters. In fact, you could claim that the basis of all intelligence and thought is rooted asking 'why' or 'why not'. It would not be wrong to say that thought is the opposite of conformity, and conformity is the absence of thought. (The garden of Eden story, with the fruit of the Tree of Knowledge only being obtainable via rebellion is an interesting ... corollary to this.)
So we have two conflicting instincts: Conformance and Rebellion. We tend to either deify the one and hate the other, or despise the one and worship the other. But this is a mistake. Both are valuable. Sometimes running like a panicked lemming is a good thing to do. Sometimes spitting in the face of tradition is a stupid thing to do. The trick is knowing when to do which.