Because they bring absolutely nothing new to the comparison. These languages are uninteresting in their feature set, and plain boring compared to Forth. Python and C++ already represent the "most used" languages category.

Also, not knowing Forth is a Bad Thing(tm) if you want to be a Real Programmer(tm). Same goes for Lisp and Prolog. They all have a place in the history and practice of programming, and dismissing them as "obscure languages that no one uses" misses the point.