This is also true, but I think this thread points more to a systemic problem in RPGs: characters not central to the overall game/plot are not given the same level of depth as characters that are, even though screentime and the existence of dialogue may lead one to believe these characters are more important than they actually are. Just because the plot device has a face and a voice doesn't mean the plot device is meant to have the depth of a character.
As someone who has been DMing and playing in various iterations of D&D for the past thirty-something years, I can absolutely confirm this happens at the table just as much as it does anywhere else.
