By doing so, he makes the setting vivid in the minds of his players, thereby connecting them to it in an important way. That s an important way to guarantee a campaign s sustainability. Another important element of a setting s flavor is the non-player characters that inhabit it. NPCs are as important as the other parts of a setting. In some ways, they are even more important.
Player characters interact with local NPCs in a way that they don t with buildings or terrain.
NPCs are the GM s voice and are an essential means by which he conveys the look and feel of a setting. Or perhaps not. If the GM has done his job right, the players may well become attached to the other elements of a setting. In the end, it s familiarity that s the important thing. The players need to begin to think of their small chunk of the universe as home .