> Computer UIs need animations for the same reason they need shadows, gradients, and momentum:
The thing about design principles is that the designer picks the one that justifies their decision, which is more like fashion than anything.
For example: Windows 8 swept away shadow, and semi-transparent material in the name of flat design, making it resemble Windows 2.0. Windows 10 brought back shadow. Windows 11 brought back Semi-transparent material and also rounded corners buttons from Windows 2.0.
Gradients have been banished and missing for a decade, but I am waiting for a come-back.
> because these are aspects of the physical world that we already know how to interpert, so can be used "for free" to aid our understanding of the UI.
The above could also apply to more than just shadows, gradients, and momentum.
Skeuomorphic icons help users understand functions but we have shape & outlines resembling hieroglyphs. I doubt we are getting skeuomorphic icons back ever because font icons are just too awesome for designers.
Most real world buttons are elevated off the surface to let us know it is pressable, but digital buttons now just have a white or colored pill shape around it. I can't recall the last time I saw a pill shaped button in the real world.