The "Why an animation for a still?" thing isn't that difficult to work out, I would say.

The object is modelled in one particular way (to fit the figure's zero-pose, usually). The picture you want has the figure in some other way. You need the in-between frames to allow the object/garment to change from one state to another. It can't be done instantly because the effects of gravity, etc, take place not only in three dimensions but also in time. The longer something is hanging, for example, the more it will want to drape straight to the ground. This has to take place over time, and time is what the animation timeline is all about.

It's not really an animation as such, it's just getting the object to move from its modelled state into the state you wish it to be. (In theory.)