Stay off the set!

We might not often see the editor on set.  Maybe this is because the Director doesn't like them, or because there's very little reason for them to be there.  It may be a mix of things, but now I understand that perhaps the biggest reason is because an editor does not want to see the film being filmed.

An editor's job at it's most basic is to match the shots in an understandable way so that an audience can view them coherently.  An editor does not want to see actors out of costume, things on set that weren't in the frame etc.  This is because this is what an audience sees and an editor wants to deliver the best possible vision to an audience without the distraction of what he has seen on set be play a part.