No. Some of us work even more focused on a single smaller screen even than having 10 BS windows asking for our attention (and I include debuggers in those, the ultimate hop-around time sink for some developers).
Besides, people managed to write software for several decades before larger than 14" screens became the norm. Heck, until the late seventies many people didn't even use a visual editor -- they only edited their files line by line in ed. And until the 90s even color was not that common -- there goes syntax highlighting (and many other uses of color).
So I don't think big monitors are any sort of necessity in the days of 15" laptops with excellent retina screens.