It's not about monitor size or resolution - text just gets hard to read once lines exceed a certain width, because the eye starts losing track of which line it'

It's not about monitor size or resolution - text just gets hard to read once lines exceed a certain width, because the eye starts losing track of which line it's on as it sweeps from the end of one line to the start of the next. That's true for prose as well as code - and code has the additional complexity of having to keep track of possibly-deeply-nested paired pieces of syntax (parentheses, braces etc); that part can be made easier with indentation, but not if everything's on one line. Wider screens still have their advantages even if you keep your text narrow, mind - when you want to display multiple things side-by-side; the halves of a diff, or your code & a reference, for example.