video format usually take up too much memory: what you gain in efficiency costs in resources.
Conversely, animated WebP are dirt cheap: one buffer only, written over and over.
Then, there's optim being made in WebP to allow fast jump to keyframe, even when there's transparency. Video codec don't allow that, and you can have an arbitrary long torture sequence of transparent frame that needs to be decoded back when the video comes in the view again.
Last, animation are usually low-fps (~10fps): there, video codec don't perform very well and are basically keyframes. So the difference isn't as great as one would think.
Oh, and hardware need a 'reset' between decoding tasks, to reconfigure memory, and decoding can't be parallelized.
Then, there's optim being made in WebP to allow fast jump to keyframe, even when there's transparency. Video codec don't allow that, and you can have an arbitrary long torture sequence of transparent frame that needs to be decoded back when the video comes in the view again.
Last, animation are usually low-fps (~10fps): there, video codec don't perform very well and are basically keyframes. So the difference isn't as great as one would think.
Oh, and hardware need a 'reset' between decoding tasks, to reconfigure memory, and decoding can't be parallelized.