In practice switch bounce often lasts tens or even hundreds of milliseconds, and you need to space out the read process to cover the entire bouncing process if you want to avoid registering fake presses. Using basic averaging means your minimum input latency is going to be ~half your bounce time - which is often way too high for it to feel like real-time input.

If you want to achieve low-latency input, "act on first edge, then ignore for the switch bounce period" is a far better approach. It also conveniently solves the "press, then release within bounce period" problem where an averaging algorithm would completely ignore the button press.