The idea of a custom bike is a valid idea, but I have followed a number of custom bike stories from idea through construction and in a significant number of cases the resulting bike isn't exactly what the buyer had in mind.
So true. I think a lot of people don't know what they want, even down to knowing their size. Ordering over the net without the builder seeing one can lead to severe mistakes. Returns are a problem for both sides.
In any case one nice thing about production bikes is you can validate how you feel about a specific model based on reviews, owners reports, test rides, etc.. and when you get the bike you can expect the product to be the same as the bikes you researched.
I think that kind of thing exists with customs that are well enough known, but stock bikes should have more buzz and the consumer thing is a lot cheaper, so more bang for the buck. In some areas, people are buying stuff mostly to participate in the buying and reviewing thing, and not the doing thing. Came across this from knife makers, where understandably few people really need a survival knife say, but they buy the stuff and "test" it as they read about it being tested in the magazines.
With Surly, and a few others, they are actually doing more interesting bikes than the custom makers. There are probably a lot of custom builders (established in particular) who would not have wanted to do the Big Dummy, or Pugsly. They have their own groove, and the cost of doing weird bikes one off, with special wheels is too high. And what client would have asked for it. So in certain cases the stock guys are more fun.