Presented like this it may appear that the app is just a series of waits, it’s not. Most of these indicators are actually on the screen for just seconds, but that is sufficient time to quiet a user’s doubts and ensure they know things are working. It feels great to click through the app and always feel like you know what’s happening, that things are working. We use prominence of these indicators to tell people how important it is that they wait. The amount of surrounding UI is a clue about what else they can do if they don’t want to. You certainly have to wait for the app, itself, to load. But you can pass right by a To-do list that’s fetching a preview of it’s items. Just the right UI feedback makes sure users know this without having to think about it.

https://signalvnoise.com/posts/2771-providing-great-user-experience-with-feedback