I think this is so often mentioned, because of AI/Lisp's common history. I am in natural language processing (which is sometimes seen as a subbranch of AI) and I have rarely seen anyone who used Lisp (mostly Perl, Python, Java, Prolog, and C++). Also, most machine learning software is written in C, C++, Java, or Matlab, with a strong and growing Python presence (via NumPy/SciPy).