Because the majority of those people never had the opportunity to work with Smalltalk, Lisp Machines, Oberon, Amiga,...
So they look around and see only UNIX CLI.
It is just like mankind during the middle ages that never experienced how the Roman and Greek society were developed before the empire downfall.
edit: the comment by zorbo seems an interesting answer to my question, but I'm still not 100% convinced; also, I must still ask how can we be sure we're not victims of a text-mode "Stockholm Syndrome" in this regard?