Throughout my group fitness classes, I pepper in a healthy amount of imagery. The reason for this is that an image can convey a large amount of information instantaneously. Ultimately, it is a tool to make more movement more accessible. Explanations devoid of imagery involve large amounts of technical information and in-depth descriptions, which can sometimes be confusing to participants.
Many people who come to classes are not as familiar with anatomy. By employing effective imagery, misunderstandings and breakdowns in communication can be avoided. From the perspective of a group fitness instructor, this tool requires good understandings of the movement mechanics, of human science, and of each person being cued (modifications vs. progressions).
Common cues typically focus on the arrival instead of the full action of the exercise. E.G. When saying "Grow tall through the spine," how else can we get there when applied to our own physical experiences? In this case, we could swap that with "Reach the head away from the tail like a telescope." Sometimes, finessing the imagery can allow participants to better connect the dots throughout each exercise.