Spinners can be helpful when you want to ensure that data is loaded before a user either exits the app or clicks on something else which can cause some havoc. I dove into spinners when I had an end user, who was entering a large number of records and would close out of the app before the ants were finished marching (the app loaded all of the records successfully.) This created both some data issues and poor user experience. There are two options for spinners in PowerApps, the out-of-the-box page spinners and using GIFs.