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[Edit]: Thank you kind stranger.
Again, just guessing, but I would imagine that it’s managing that state and animating it in a sane way which requires LOTS of code, less so the animations themselves.
Animations are so often an ill-advised, interaction-slowing pain in the ass for users that I'm curious about beneficial and non-annoying use cases.
I think it depends on what the goal of the screen is. If the goal is to simple provide information to the user, it makes sense to have clean, simple, and snappy animations.
However, I think there are also situations where the experience itself is the goal. i.e. give the user a visually pleasing graphic, animation, interaction, etc. In this case going a little wild with animations can be a good thing.
Most in app situations should be the first (snappy, clean, useful). But selectively sprinkling a few instances of the second throughout your app can bring the experience to the next level.
In our case, we wanted the rewards flow (it's a banking/brokerage app) to be a fun, gamified experience to separate us from typical banks. So we opted to add a very visual, interactive experience in this single part of the app. There's a demo video above. While it's certainly extra, I think it makes the core flow of the app a unique experience.