Written records mostly capture people who held power or kept files, so the experiences of ordinary people go unrecorded. Asking people to tell their own lives in their own words brings into the record what documents leave out: feelings, family relationships, and the unwritten customs of the workplace. Without such testimony, the history and sociology of an era stay poor and narrow.
What people remember and how they tell it is bound up with who they are and who they take themselves to be. A life story is therefore both a report about the past and an expression of the teller's present self. Interpreting it means attending to how memory, self and identity shape the account.
When the voices used as evidence widen beyond the powerful, history covers more ground and its social message changes too. A past built from many people's testimony becomes more democratic, and this challenges the settled myths of official scholarship. That is why the method meets resistance from more conservative academics.