I think you might have nailed it. Unfortunately, my eyesight is less than perfect - for example currently my screens are closer than arms's length from my eyes

I think you might have nailed it. Unfortunately, my eyesight is less than perfect - for example currently my screens are closer than arms's length from my eyes (granted, I have pretty long arms). So, in my case, the bigger monitors would force me to do neck movements, while for people with really sharp eyes they could be great.