Yes, it has been shown that women and men actually speak the same number of words each day, but that doesn't mean that we have to give up super-clever jokes like this one:
Get it? It's funny because girl-people are so different and incomprehensible and other. Sure, it might not be 'scientifically true' that women talk more than men, but it just feels so true - probably because we've been exposed to jokes like the above our whole lives. But, if we let our stereotypes give way when presented with evidence that should disprove them, then we might have to think up new jokes - and no one wants that.
(h/t Language Log)