I never said that a video editor would be the same kind of authority on sound as a real sound engineer or producer. The issue at hand was: are cans used in professional studios? The answer is: yes, they are a very crucial part of film/video production. I also never said cans should be used as the sole source of reference, I meant that they are a reference amongst other references and certainly an important reference considering how many people use cans to listen to music. Either way, I do believe we actually agree on most accounts, so I'm not looking for an argument here, Just trying to clear things up.
With all due respect, yes a number of video editors use cans for sound (and poor speakers in poor acoustics), that is one of the main reasons why they produce lower quality audio results than an experienced dubbing engineer in a well designed and calibrated mix room, where all mixing and dubbing is done through speakers. BTW, cans should never be used for referencing unless you are creating a product primarily designed to be listened to with cans.
To the OP: Bare in mind that a studio today is not quite what it once was. These days, anyone with a sound card, a mic and a computer in their bedroom can call themselves a "studio" and if they've charged their mates for editing and burning a CD they can also call themselves "professional". So using the title of "Studio" or "Professional" does not necessarily mean very much, beyond marketing. Jupitreas is correct that cans are used for several purposes in professional use. Recording studios always had a few pairs of Beyer DT100s around. DT100s had truly dreadful bass response, which made them ideal for providing a musician with a cue mix during recording, as there was very little bass to spill back into the microphones. Apart from a few specialist applications like this, you are right when you say that headphones are not used much in studios.