Think of anything that you have to keep remembering to do with your phone. For example, I turn several settings on or off every time I leave the house or return home. I use Routines for some of these and Bixby Quick Commands for others.
Maybe there's a some function on your phone that you'd like to have a button on your desktop for. Flashlight is popular with many users from what I've heard. I've added several buttons to my desktop for functions that are available in the Quick Panel - I just find it quicker and easier to have these in Routines desktop widgets instead (flashlight, battery saver, Bluetooth on/off, etc).
