Scrollbars
I never really noticed when the scrollbar started fading away, but during my lifetime, I watched it grow thinner, begin to fade when inactive, and finally only appear with a cursory movement. Eventually, this behaviour became the default, an interface element that exists only on demand, no longer a fixed part of the screen.
Thoughtful piece where the visual experience serves to highlight the point made throughout the essay.
After reading I've changed my system settings to always display the scrollbar.