Luke carefully tells the reader that the dead young man at Nain is his mother's only son and that she is a widow. Those details make the scene socially as well as emotionally devastating.
Jesus meets the funeral procession as the body is being carried out of the town for burial.
Burial commonly took place soon after death in Jewish communities, often outside the inhabited area. Mourning was communal, and Luke notes that a considerable crowd accompanied the widow.
A widow could depend heavily upon adult sons and other male kin for economic protection and representation. Not every widow was destitute, but the loss of an only son could remove an especially important source of support and continuity.
The background deepens Jesus' compassion in the scene. He is not restoring only a life; he is returning a son to a bereaved mother whose social future has also been imperiled.
Luke's concise description therefore prepares the reader to understand why this particular funeral becomes such a powerful public sign when Jesus stops the procession and gives the young man back to his mother.