There were shepherds in the same country staying in the field, and keeping watch by night over their flock.
Abiding in the field ...  The fact of the shepherd being outdoors suggests the temporal and transitory nature of the human family's status on earth.  In the larger context of man's earthly tenure, the shepherds were better representatives of mankind than dwellers in strong houses might have been.  In a sense, all men are "in the field," subject to all limitations of earth life, and remaining but a brief span of time.