Animations give you clues as to what is happening and how to undo it. A great example is the macOS “genie effect” when minimising windows. A first time user who clicked the minimise button on a window and saw it simply disappear would be lost as to where it went or how to get it back. Even as it appeared on the Dock, the lack of animation there as well could be imperceptible or the user might be unable to see what changed.

By having a clear animation which indicates where the window is being moved to, it’s obvious where the window went and thus how to recover it.