This is, I agree, an interesting phenomena. I feel that the answer to the mystery as to why 90% of people drink the mainstream crap, is targeted marketing. Sounds simple, but think about it.... all the crap that people buy but do not need is filling a need that they suddenly have... People need beer for many reasons (social, taste, etc), but they *BELIEVE* they need to choose BMC as that is what everyone says is the popular choice (not to mention commercial ad campaigns etc feeding into the fact that people are lazy, and the quickest route to satisfaction and filling the social need of acceptance is going along with a popular choice).
But... I regress. If major BMC had some kind of limit to their ability to market and hog the market out of pure buying power, we would not live in a capitalist 'free market' and would probably be in china or something... nothing against china here.
So, IMO, we cannot live without crappy brands that most people buy simply because they are too lazy/dont care to explore complexity because it is part of our society's nature. Imagine how scary the "ignorant" masses were in medieval times? Dont even want to think about that...
Rant over! NOthing against those who drink the stuff personally, I hope I did not misrepresent.