It's not just about having UI. Services have their separate uses like it runs in the background until you tell it to stop. It means it can fetch data from APIs or images in the background thread and can pass this data to your activity. I know android has much better options for doing these tasks but you can do almost anything which needs to be run on a background thread. Another use of service comes in my mind is running a service in background which waits for particular action like incoming call, system boot, etc.