It would if you didn't care. If there is a situation which arouses your interest, you'd have to watch and take input. Both require a lot of "nerve" energy (especially the eyes). You would then have to check the new information against your worldview, which can also be relatively high energy.

I guess, many people just want to spend as little energy as possible. So, of you convince yourself, that the truth/world is the way you believe it is (=prejudice), you don't have to spend any energy, neither observing nor verifying.