... if you know how to use virtual desktops and shortcuts. You can't look at two screens at a time, anyways.
One use case I can understand is having a 2nd monitor for checking stock prices or checking for a certain event. Other than that, I don't see how it contributes to "productivity" while working or coding for example.
P.S: Tiling WM users may understand this post more
Lol an actual unpopular opinion. I use 4 monitors. Sometimes I'm looking at reference documents on a second monitor to determine how to implement the function. Sometimes I have my dbms app up on the third screen so I can look at the data structure as I'm implementing it. And the 4th monitor is usually for YouTube so I have a background noise/video to keep me focused