Lisp is significantly harder to learn for most people--especially those people who are programming only as a means to an end and not for fun.

Lisp goes significantly farther towards shoving FP down your throat than Python does any individual paradigm.

Lisp does not (to the best of my knowledge) have anything to match scipy/numpy.

Now, this doesn't mean that I wouldn't prefer if the scientific community were dominated by FP instead of Fortran and Python, but I think it's very easy for people like us to go and say "FP is easy" without realizing that for most people it's really not.