Well, I think because the population at large doesn't seem to be able to confront their own psyche, and that the advances and discoveries in science are pointing to a material irrationality. The materialistic, monotheistic, existential paradigm is what is in place in the world at large, which led us into a growing crevice of repression upon repression to the point of utter terror of the unconscious and any question which lies outside the contours of the ego, not to mention a mechanistic aversion to any ideas (not paradigms or ideologies, but IDEAS and visions) that are out of the ordinary or marginalized. The truth is beyond auditory language as symbology at this point. The leading discoveries in physics point to the idea that an observer is necessary for a physical event to take place, on top of the nature of matter being particles? Waves? I know next to nothing about physics or any kind of science and what I'm frankly regurgitating may as well be complete bullshit. Likewise, any idea of prophets or gurus is out of the question; a circumstantial talent to articulate the accumulated information (which I think people like McKenna and McLuhan had, and were subsequently banalized by the media and the internet respectively) about our position within evolution and simply communicate it with people is the virtue, because, through psychedelics and the internet, everyone is a guru, no matter what your age or appearance. The internet is an anonymous cradle of information, and this information includes historical and contemporary writings on the transcendental experience, which blasts one out of the materialistic, monotheistic existential predicament. The egocentricity which naturally accumulated in public speakers about these issues in the past is precisely what seemed to lead them into dead ends, since their message was the realm bereft of ego. In any case, this repressed mass culture is not on par with the flow of science and technology, which is expanding its possibilities, densities of information and leading us into very strange territory which stands teetering on the line between the objective-material and subjective-symbiotic worlds. I think the singularity may as well be something as simple as human beings and their environment. I think the idea of the end of history is very valid; every historical culture, movement and event had no point of reference to other cultures, movements and events from the past. Now we're headed straight towards a global shopping mall based on a dominator hierarchical system, ever divided.
I think McKenna's summary in a nutshell is the stressing of EXPERIENCE over SYMBOLIC EXPRESSION and the construction of a community which shares this value in EXPERIENCE and uses language loosely and not ideologically to create a sense of being in this together instead of being an experientialist alienated and subsequently swallowed whole by the nihilistic consumer culture.