Many animations are simply stylistic, but others convey information.
Any animation that gives you "almost there" information about a gesture; fro example, holding your finger on the screen in Minecraft PE starts an animated circle. When the circle completes, the action is complete. It provides extra information.
Ditto for the "swipe right to delete" animations in iOS mail; the animation lets you know which side of the "show options vs delete" wall you're on, and how close to the edge.
Any animation that gives you "almost there" information about a gesture; fro example, holding your finger on the screen in Minecraft PE starts an animated circle. When the circle completes, the action is complete. It provides extra information.
Ditto for the "swipe right to delete" animations in iOS mail; the animation lets you know which side of the "show options vs delete" wall you're on, and how close to the edge.