Because no argument is good without an irrelevant personal anecdote:
At my current job, we do use Python for some stuff. We also have (and have had) a couple of “junior” developers. None of them had touched Python before, and I tell them, “yeah, just read the Tutorial” (note the capital T there). Some read it, some don’t. Those who did read it started putting out useful code in a couple of days.
In a hypothetical situation where you replace Python with Prolog, what do I tell them? I honestly don’t know. And this is vexing me greatly, because SWI-Prolog is a better tool than Python for about 2/3 of the cases in which we currently use Python.
EDIT: now that 3 more years are gone, I could re-visit my incomplete work and see how I feel about it now. Don’t hold your breath. I have two other things that are very high priority at the moment. Maybe, if I can show something and say “this is what I meant” it would be much easier to judge whether it is a good idea at all.