* Loading indicator - from a UX perspective we are used to this so having a non-animated loading is weird. I think gmail used to do it but that was back in the mid 2000s.
* Confirmation of a user action - if I have sent an email then a sound and/or animation can feel good. It is not necessary but sort of adds a magic to the application.
* Where the animation is useful in explaining something, for example, an explanation of balancing trees.
We shouldn't use them on:
* Static "non-app" information pages / landing pages etc.
* As a button icon pre-action. E.g. the word SUBMIT sliding from side to side would be annoying!