That kind of defeats the purpose of having software controls. You can as well unplug the whole thing or remove the battery violently on a laptop and claim "it's still as straightforward as before!".
How do you interact with software? With keys/buttons. Think of power button as another key. Microsoft conditioned all of us to never ever touch that power button, but it is all right now. I promise.
The power button is a software control. It generates an interrupt, and the operating system shuts down the computer. For all purposes, the exact same deal as if you hit the software power button.
