Apart from inspiring visually similar images in the reader's mind, they also have thematic similarities as well. Just like the dew, the bodies from which souls depart are fleeting and exist for a relatively short period of time. They're also immensely fragile: the sun evaporates even dew that's shaded, and the corporeal figures that hold the soul are just as vulnerable. This also underscores the favorable meekness to dew that a Romantic like Hugo would have appreciated as a desirable analogy to humanity's sublime minuteness.