As a computer programmer, I can see why a dual screen setup can give you several advantages over a single monitor setup. You could be looking up documentation on the right screen, while writing code on the left screen. You could also be chatting on one screen and surfing the web on another.
I currently have 2 monitors. The reason I use the second monitor, is to display my calendar and various information about my system, like cpu/memory usage, todo-list output, chat notifications, etc.
I can work on one screen and look at my schedule on the other.
But this week, I have experimented with simplifying my setup, by turning of 1 monitor. They say "once you go dual monitor, you never go back". I can agree about the benefits of a second monitor, but there is one disadvantage about it: it takes up more space on my desk. And because I'm constantly decluttering and following a journey towards minimalism, the idea came to just turn the monitor off and see how much I would miss it.
So far, the absence of the second monitor hasn't bothered me much. I use Arch Linux as an operating system, with dwm as a window manager. That's a minimalistic linux distribution with a very minimalistic window manager. The important thing about it is that you can have multiple workspaces, that be used to replace the functionality of the second monitor. (Actually, the second monitor was brought in the picture to replace some functionality of some of the workspaces, I'm just switching it back to the old system).
If I can manage to keep this system, without actually needing the second monitor, I can sell one monitor.
This would free up space on my desk. And that in turn, would eliminate the need for such a large desk, leaving me with the option to get rid of the desk and replace it with a smaller one. Which in turn would give me extra space in my small room.
All in all, it's an experiment worth trying out, considering the benefits it would give me.
Minimalism... finding out what you don't really need, getting rid of it and focusing harder on what really matters. In this case: one monitor.