User blog comment:Kirkburn/The expanding world of the VisualEditor/@comment-24001421-20141003222730/@comment-126761-20141009130418

The VisualEditor itself is intended to match the article space exactly, so it's shows a true representation of the saved page - making it larger would break this concept.

However, if you're referring to the source mode dialog within the VisualEditor - yeah, this is something we do want to look at further.