Over the last 10 years, I've migrated from three screens down to two screens and am currently down to one and a half screens. (I currently run my code editor and a browser on a 4k monitor and airplay to my 11" iPad where I keep a terminal app fullscreened.)

I think it's because resolutions have gotten better. 2010 I was running one screen for editor, one screen for browser, and one screen for everything else.