- Device provisioning - Automating a device right after power-on to do initial set-up, add to Wi-Fi, install apps, etc. (Other methods, like ADB, have to be enabled first. Who does the enabling?)

- Security testing - Interacting with a device that may have malware on it. You use a robot so that it is 100% unmodified while you study it. For further safety, the device is run inside a Faraday box, and you use the robot to access the device from outside. (Otherwise, you do everything manually in a human-sized Faraday cage.)

- Performance testing - Getting timing data of app performance is more accurate when the device is unmodified and you use an external tool to interact with the UI.

- Testing medical devices - Required to be tested exactly the way a user would interact with the device.

- Point of Sale testing - Some real world end-to-end tests involves inserting or tapping a card and entering a PIN on the screen.

- Or you're interacting with a touchscreen that has no other programmable interface, but you still want to test automate it (like any touchscreen on any device that is not a phone or tablet, e.g. an HVAC or alarm system panel.)

(These are all things I've been paid to make robots for over the last decade.)