In the best of those languages the user is getting input and output through the diagram in realtime. Also, syntax errors are either removed completely or conver

In the best of those languages the user is getting input and output through the diagram in realtime. Also, syntax errors are either removed completely or converted into runtime errors. These features allow the user to iterate rapidly through the development process to create a prototype, perhaps even gaining an average 100x development-time increase over using a compiled text-based language. The spaghetti is evidence of that-- the user moved so quickly that they were able to hold the relevant abstractions in their short term memory to produce the final write-only diagram. And at least in my experience, the final write-only diagrams tend to work to produce the desired output, even if they were written a decade ago. In fact if there were a button users could push to "abstractify" some pre-spaghetti sub-diagram I believe that would negatively impact the language. The point is that when you've got mental model of all inputs and outputs within a single page visual cheat sheet, you can instantly connect any input to any output to take the next step in the development process. For certain domains like audio synthesis the fact that the user can leverage the diagram-based system to get any output at all is worth the seemingly prohibitive price of write-only programming.