Kind of a weird example but RpgMaker is a tool that lets non-programmers create their own RPG games. While there is a 'text based code' (ruby) layer a non-programmer can simply ignore it and either use modules other people have written or confine their implementation to the built in functionality.
Now look at the complexity involved in the application itself to enable the non-programmer to create their game. Dialog boxes galore, hundreds of options, great gobs of text fields, select lists, radio buttons. It's just overflowing with UI. And making an RPG game, while certainly complex, is a domain limited activity. You can't use RpgMaker to make a RDBMS system, or a web framework, or a FPS game.
The explosion of UI complexity to solve the general case -- enable the non-programmer to write any sort of program visually-- is stupendously high. WIth visual tools you'll always be limited by your UI, and what the UI allows you to do. Also think of scale, we can manage software projects with text code up to very high volumes (it's not super easy, but it's doable and proven). Chromium has something like 7.25 million lines of code. I shudder to think how that would translate into some visual programming tool.
I'm not sure how well it would scale