Perhaps great programmers are great in any language, and a company employing great programmer will have great results in any language, it’s the programmers that are the competitive advantage for a startup.
But although they’d be great in any language, they have taste, and prefer to work in some languages regardless of whether that is a competitive advantage or not. And therefore, they prefer jobs and startups with languages that match their taste.
And taking that a step forward, these mythical great programmers might prefer working with other people they perceive have taste, so they tend to clump together, and they see the language choice as a kind of signal of what kind of colleagues they will have working for a particular company.
If all this handwaving has merit, it could be that choosing to do your startup in Lisp when Paul started ViaWeb was’t 100% about having a competitive advantage from Lisp itself, it was having a competitive advantage from having Paul and Robert, and anybody else they hired.
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With larger companies, they will never say it, but sometimes they don’t want these “great programmers,” with their taste and their salary demands, and their code that causes an army of middle-of-the-road workmanlike programmers to stare thoughtfully for long periods of time working out how it does what it does.
Even if they end up being more productive, perhaps they end up being less predictable, because a smaller team of better programmers is more vulnerable to poaching as the company goes from developing the next big thing to an endless march of adding small enterprisey features. Even if you write in Scala, Haskell, Lisp, or Clojure, when the work becomes maintaining Yahoo... Maybe you don’t want people who relish a challenge, because they’ll quit.
So you want to anti-signal, by rewriting it all in a workmanlike language, so you get workmanlike people. And if it takes touch longer or costs a bit more overall, it’s predictable because the people are more fungible. They’re easier to replace.
So it could very well be that when you’re launching a startup, you want to go out on a limb and choose the language based on the kind of people you want to hire for a startup.
And when you mature, you might rewrite it in another language based on the kind of people you want to hire for a mature company.
And both choices might be right for their times. And neither might actually have anything to do with the “power” or “expressiveness” or “abstraction” of the language itself.