Families that have lived in an area for generations can often trace their roots through the local church and its graveyard. Centuries of weather may have obscured many of the headstones, but they are still there. Modern methods can often be used to decipher some of the letters that were originally carved. The local church may also have written records for most of the years since they were founded. Tracing a family line in this manner may be the only record a family can find.
It is just in the last century or two that the majority of people have learned to read and write. Before education was widespread, many priests were the only literate record keepers for many areas. They kept records of births, marriages and deaths. Even governments have not always been able to keep records as well as the local priest. When seeking a family history, the local church may have the best records available.