Creating an impression of a scene or film sequence is always something special. In this sence it can be the most important moment that needs to be designed and layed out as a keyframe or even a sequence of frames to illustrate a specific storyline.
Sometimes, a styleframe helps to create context for a concept of an object or character, that furhter describes it. Often, key or style frames go through a longer process with many feedback loops. Additionally, a big advantage of such illustrations is that you can experiment with different scenarios before making a decision on a specific direction. This way, possible solutions and variants can be ruled out.
I have also often developed matte paintings from styleframes and was able to achieve a direct transfer from pre-production into the final production of a shot, which significantly accelerated the whole process.