Why does Chaucer treat love different ways in The Canterbury Tales?
Chaucer's presentation of love varies from The Wife of Bath (and prologue) to The Miller's Tale, and The Franklin's Tale in terms of the genre of French Romance: especially Marcabru's moral dichotomy of fin' amor vs fals' amor, Chretien de Troyes idealistic conjugal love, and Marie de France's realistic attitude towards adulterous love. Why does Chaucer treat the subject of love in these three different ways?
I believe this question can be answered fairly simply. You are right in that Chaucer did present several different views of love in his tales. He actually also addresses familial love and love in friendship, as well.
As for romantic love and what you address above in your question, Chaucer most likely addressed love in different ways to show that love represents many things to many people and that love is fickle, complicated, difficult, but also wonderful, exhilarating, and all-consuming. By showing the reader these different views of love, he paints realistic, not idealistic, portrayals of love and how it can also change and grow or die at various time.