Well, basically, it`s the same thing with dieting(and religion, but I don`t want to go there, nor will I ever on this board or any other for that matter). Tell a man/woman that in order to lean out he/she simply needs to eat less and move more...and watch them find a billion ways of rationalizing even the craziest stuff, eating their guts out whilst being convinced they eat less and so on and so forth. Invent a magical protocol that "melts fat away and builds muscle" by simply employing it-low carbs, paleo eating, you name it-in order to trick them into eating less and voila. Though counterintuitive, the correct path seems to be that of extreme complexity...because ppl need to feel they`re doing really important, complex crap, they don`t want the basics, they`re over the basics.
It`s the same with HST. Bryan made it more than fool proof-he formulated basic ideas in a very appealing manner, he ensured that all of the important aspects are obvious, covered, and pseudo-magical(the weight progression-most lift the same weights their entire lives, and wonder why they aren`t growing the big musclez), injury safe-guards(the 15s), "forced" lay-offs(forced as in making them look like really really advanced stuff, because otherwise, were he to simply appeal to common sense, most would`ve screamed OMG Ghey or something along those lines), optimal frequency(actually a minor compromise here, as 48 hrs may be a bit on the overestimating side of things WRT protein synthesis et all...if you train AM/PM though, you`re in the 36 hour sweet spot) etc. And ppl are still screwing it, can`t build a program by simply using the universal principles(which existed before HST, though not as coherently put together), and even in light of their own idiocy, blame the program. That`s how we work, God was a joker.
So yes, psychology is hugely important, but again, and I think you`ll agree(and I finally see your point) no matter how you drape it, putting a nail through a skull is still stupid(an example)
Training in suboptimal, misguided and dare I say asspulled ways is still an inefficient, crappy way of building muscle(if you actually manage to build anything beyond the begginning growth spurt), no matter how much you believe in them. I guess what I`m saying is this(and it`s the same with diets, IMO):start with physiology, set everything up to be as optimal as possible WRT what we know about the human body/what works, then add the mystical layer meant to induce adherence. It`s what Bryan did. It`s what Lyle does. It`s what Kelly Baggett does. And there are a few others.