Whenever a user interactable element will be ready in <~100ms, you can display it as ready now, because it is faster than the reaction speed of a human, which makes all interactions with the software faster, smoother and more responsive than if I used a loading indicator. It's a free win.
Whenever you know in advance you need to display something to the user and need to load/process something that takes much longer than 100ms, you can load in the background while displaying whatever needs to be displayed and if the time spent on the screen is slower than the loading time then the next interaction will be instant (common case), if the user is faster on the screen you can still go to a loading screen, but the time it is on screen for would still be much much shorter.