Checking the button state a bunch of times and computing an average wastes a ton of clock cycles that you could be doing anything else (like updating a display, polling sensors, etc).

The standard way to debounce is to attach an timer to the button. When you press the button, an ISR runs that temporarily disable the timer from triggering again and starts the timer for a specific period (say 20ms). The processor is free to do whatever it wants for the next 20ms. When that timer expires, another routine checks to see if the button is still being held, sets the button's state accordingly, then re-enables the button Timer so it can be triggered again.

Averaging loops are much better for analog inputs where you may have noise that throws off the reading. You only care about a button being on or off, it doesn't matter if it's been mostly on for that period only that it's still on.

When you get into extremely fast digital inputs that need to be reacted to sooner than the debounce wait period, that's when you need hardware debouncing.