I believe the answer is: Fieldwork allows anthropologists to be exposed to a variety of new opinions, perspectives, and ways of looking at the world that help us better understand the opinions and ideas of others while simultaneously influencing our own outlooks
When a certain anthropologist observe a certain culture from outside perspective, there would be a couple of information that the anthropologist wouldn't understand since he/she does not embodied the culture. After doing a fieldwork such things would be seem more relatable, which would deepen the anthropologist's understanding about that culture.