> I've never understood why we still look at the plain text representation of code, and not a visualization of the code that makes more sense.

My guess is it is the same reason why the most common form of creating source code is typing and not other readily available mechanisms:

  Semantic density

An example of both are the emacs and vi editors. The vast majority of supported commands are at most a few keystrokes and any programming language source code can be manipulated by them.