It provides Chaucer with an opportunity to write about characters that represent a wide range of SOCIAL classes.
Take the Pardoners Tail for example.
The Pardoner describes a group of young Flemish people who spend their time drinking and reveling, indulging in all forms of excess.
or
The Wife of Bath.
The tale concerns a knight accused of touching a woman inappropriately, whose life shall be spared if in one year he discovers what women most desire.
Both of different social class.