Well, I've already gotten a few comments from family members asking why I need a 2nd monitor for work. The answer is simple: I need it for a bunch of things.
We are currently making some new Farmer Fern videos and changing items on the website. Having 2 monitors cuts the time almost in half. Any time there's something I need to Photoshop or cut up or code into the site, it gives me the ability to do it extremely quickly. Even when I'm only doing something on 1 monitor, having the second monitor available lets me see updates on GRF or have my music player up without me having to switch back and forth.
All in all, it's extremely useful and only added $100 to the price of my setup ( I bought a Walmart brand monitor). It's a worthy investment and if you have the chance to increase your productivity, why not?