I actually really agree with your logic Huseng - it seems to be a matter of upaya to fit 'fluidly' (pun intended) into society. Having a beer or two, especially in places like Japan, would seem to be part of this.
However, I find that personally, even one beer has a very detrimental effects on my concentration and cognitive ability (not just at the time, for an unreasonably long period afterwards). I think that alcohol is a very powerful drug - it effects physiology in very robust ways - and it seems to me, in ways quite contrary to meditative concentration, sharp perceptual discernment, reasoning ability etc.....all of which are core elements of Buddhist practice. For that reason, the precept makes a great deal of sense, regardless of its genealogy.
The caveat, is that this is just based on my particular physiology and (meager) meditative/cognitive abilities. I assume it would be different for someone like Trungpa [insert ten page controversial thread here:].