i use them for hard poses and angles, panels with multiple characters that appear on many panels in different angles. helps greatly keep things consistent and highly increases productivity working on webcomics.
In addition to what everyone says, you can save the model you edited for later use (i made a model to-scale for all my main characters).
If posing models is intimidating for you, you can look up pre-made poses you like from the Materials available (or the Assets website, most for free) and just drag and drop the pose to your model and that's it.
Even more interesting feature is "Pose scanner" using photos and the AI will try and replicate it to your model. it works to a certain degree but definitely has a lot of potential!