They were very useful for theory building
They aim at an analytical and integrative description which will bring out those features of the social life which are significant for the understanding of its structure and also for general theory.
Earlier accounts of primitive life were mainly given by travellers and missionaries who found the customs of the primitive people unique and strange. Similar was the case with the Christian missionaries.
In their objective of conversion of the primitives to Christianity they found very strange religious ways which they reported to the civilized world as anthropological monographs.
During the middle of the 18th and 19th centuries, the European colonization of America had been widely expanded; British rule had been established in India, Australia and New Zealand, and many parts of Africa had been settled by European emigrants.
The character of ethnographic description of the peoples of these regions began to change from traveller’s tales to detailed studies by missionaries and administrators who not only had better opportunities to observe, but were also men of greater culture than the gentlemen of fortune of earlier times.
It must be said that whatever data were generated by the missionaries and administrators they were very useful for theory building by the later anthropologists. The new information generated in this way was sufficient in bulk and quality for Morgan, Mclennan, Tylor and others.
There was also a sufficient body of knowledge for speculation to be tested and for new hypotheses to be put forward on a solid basis of ethnographic facts.