Wide blurring can reflect the inability to see clearly when one is looking through fog or when one is experiencing overly bright or very dark lighting conditions. Wide softening could also symbolize an artist's perception being clouded by romance/love/infatuation. Widely softened images might create a sense that all of the subjects/shapes are interconnected, sharing the same atmosphere. Such blurring might also represent a lack of focus or interest on the part of the artist, and edges that are smeared broadly by the artist might indicate disdain for the subject or represent the subject's supposed irrelevance in the eyes of the broader culture.
Featured: Waterloo Bridge, Sunlight in the Fog by Claude Monet.