Dunno. However, I'm sure as hell not going to let my ignorance stop me from quickly pumping out some ideas:
* Python encourages developing clean, clear and well-documented code in a fast and efficient fashion = no job security for the programmer.
* Java is a competing high-level OO language with a lot of marketing muscle / hype behind it.
* Python has an unusual indented syntax which can be annoying to edit in a text editor not designed to support the language.
* When you say the word "interpreted" to a lot of programmers they think of BASIC and their eyes kind of glaze over.
* Most programs are written in C or C++ so that's what everyone learns and uses.