I notice your response was in the form of a few paragraphs of text, rather than a photo or diagram. Most conversation are "text-based". Our human brains have hardware acceleration for text processing and we're quite good at it. Since programming environments exist to make the best impedance match between programmer and machine, they use text. Language uses incredible composability to encode great complexity.
You'll also notice that while the comments are all plaintext, they're presented hierarchically as nested trees. There's also a hyperlink in your comment that I can follow easily, that's not plaintext.
I'm not saying plaintext is bad, I'm just saying that we're not stuck with 80x25 green-on-black terminals anymore, there's room for improvement using our modern display capabilities.
Why yes, we're not stuck with 80x25 green on black terminals.
Why even mention it? By the way that nested hierarchical tree is also written in text (HTML and CSS). So is the hyperlink. URLs? Text.
Check any modern IDE and you'll see similar visualizations over text based source code. I can explore my project in a tree-based outline in my IDE. I can open my classes as an UML diagram.
Our human brains have hardware acceleration for image processing as well. Limiting ourselves to text is wasting half our natural resources.
Flowcharts and LabView are old paradigms, they have and are problematic for abstract tasks (they're only good for data manipulation). What's needed is a new style of programming that combined the best of visual and textual representations. Wolfram Language [1] and Bret Victor's Inventing on Principle [2] are more modern approaches in that direction.
Flowcharts are one implementation of what you propose. Or LabView: http://www.ni.com/cms/images/devzone/pub/nrjsxmfm91216399872...