Because I have a Linux workstation and I want to have 2 screens. The iMac screen is waaay better than my main screen, which is why I want to use it. In daylight, those extra 150 cd/m2 really help
Not sure if this
helps the dual-screen desire, but to make more use of it, couldn't you install linux directly on the iMac? I did that (install pop os) recently with a Macbook Air 2012, and it works flawlessly as far as I can see. All special keyboard buttons, sound, sleep/wake, battery, trackpad (minus gestures), etc. etc.
