Ok let us see why it is actually useful.

Today, email is a new phone. You use it to discuss with someone, to get info, to ask info to several people at the same time, along the day you keep an eye on your mail client just like you stay available to answer a phone call. When you answer a phone call you still have your monitor in front of you and it may prove very useful. You have a phone on your desktop so you should have an email client on your desktop. This email client is your second monitor.

“Email is a loss of time I am definitely not going to let my employees loose yet more time with email!” OK you want your employees to be productive and as efficient as possible. Here is another use of the 2 screens. I am a control systems engineer so I make a lot of technical work including simulations and data analysis under Matlab/Simulink. It happens that I must report about this fun stuff. So I write technical notes under Word. The notes make heavy use of Matlab figures / data. So I must send the data from one to the other. I click on Matlab, it appears and Word disappears. I click on Word it appears, etc. What I want is 2 monitors, Matlab on the right, Word on the left. It is as simple as that. Moreover I can type my report and check what is going on for other simus.

In financial engineering people use commonly more than 2 monitors to follow the stocks. Even if you are in a less profitable business I am sure it will be worth it to buy 2 monitors per PC.

It is so frustrating to have 2 or 4 processors on your PC and yet only one monitor. I will end up installing by myself 2 monitors because if I wait for my dear employer I will wait for long.

By the way if you have only one video output on your card just buy a "video splitter".

You already have 2 monitors or more ? Tell us your setup !