It is the act of lighting the Chanukah lamp that constitutes the precept. Therefore, even if the head of the household is sick and cannot get out of bed, we may not bring them to him to light by his bedside and then set them down in their proper place.
In the past, people gathered at home just before nightfall. At sunset, then, the streets were full of people returning home. The sages therefore ruled that the time for lighting Chanukah candles is "from sundown until the marketplace has emptied out."