• when characters travel uneventfully from point A to point B
• when a motivation is needed for a character who only appears for a couple of paragraphs
• when you have a scene right after one time skip and right before another
• when a scene is moving at such a fast pace you don’t have time to dedicate ten words to the rain
• when a character is slow on the uptake and has a captain obvious moment for dramatic or humorous reasons
• when explaining backstory and past motivations (sometimes)

(source)