I think these days, most desktop setups only have about 2 monitors max. To install more than 2, requires special and sometimes expensive video cards. On Windows / Linux, these can be buggy if the setups change often. On Macs, it’s typically not even seen. My desktop has 6 monitors setup for day trading, take a look here.
These multi-monitor solutions have so many benefits. Typically when data needs to be read immediately. Often, just to extend the viewport of something cool, like a demo of Google’s Liquid Galaxy, with 8 Large LCD screens.