The main reason for multiple monitor setups would be, that they were cheaper than getting a single larger screen. But the general reduction in screen prices and

The main reason for multiple monitor setups would be, that they were cheaper than getting a single larger screen. But the general reduction in screen prices and the new class of ultra-wide screens gives alternative options to get a lot of desktop real estate. The only reason I sometimes prefer my dual-screen setup is, that when I have a full-screen application (vmware in my case) running on one screen, the other would give me additional desktop space like for reference documentation. I would never consider putting a normal windowed desktop application into full-screen mode. As my typical work requires to use multi-windowed applications, I like my desktop to be as large as possible.