I'd typically rather have more information about the file I'm currently working on rather than a bunch of different files open. When I'm using a text editor I'll want multiple text windows, but that's because navigation between files is much harder in that environment.
One can also have multiple views on one file (at least Emacs can) which is another good for having multiple buffers side-by-side instead of one single buffer.
And things go both ways: Some of us do have multiple 30"+ monitors and appreciate UIs that manage to utilize all that space.
Remember that responsive design doesn't just mean scaling down to tiny mobile devices, it also means scaling up to large screens.