[jordigh]

Partly it's more familiarity with Octave than ggplot, but partly also that the Octave syntax is just about the easiest there is out there. Type something, immediately see some graphs. Type some more, gradually modify that graph. The simplicity is a big selling point. Julia's syntax comes pretty close, but I'm not as familiar with it yet.

Remember that Matlab's and Octave's biggest audience consists of not-a-programmer programmers, that is, people who consider using Matlab or Octave as being something different than using a "real" programming language. I call them not-a-programmer because that's what I've often heard them call themselves, even as they write Matlab or Octave code.