I would briefly comment that Rosetta Stone has a terrible reputation among language lovers (see sample review about why most people can't learn like they did as a child), and some language lovers claim that people who used Rosetta Stone to learn a new language usually can't say more than a few words in the target language. Also alleged is that Rosetta Stone is at least rumored to originally be a Spanish course with heavy copying and pasting, and for native English speakers it works best for Romance and northern Europe's Germanic languages, perhaps because English is a mix of Romance and Germanic languages. (I would offer a half-dissenting caveat that for all the faults in the accent evaluator, the 1-2% who least need the help can profitably use Rosetta Stone to learn an accent.)
Now to the main question: Darwin's theory of evolution as originally formulated was an adaptation of an economic theory, or so I understand. In the proto-Darwinian theory of evolution, organisms survive differentially according to their fitness to the environment. The original economic version was that the marketplace would favor goods and services that worked, weeding out those that didn't.
So how can something so bad as Rosetta Stone be the gold standard, partly challenged by DuoLingo? It gives an impression of learning, perhaps, but serious critiques are readily available on the web. It also uses a pedagogy based on features of a small child's brain that are taken out well before adulthood. Related questions could be asked of Microsoft's success with MS-DOS and Internet Explorer, but I know enough of my bias not to make that my main question.
However, it seems that there are vastly inferior products on the market which are preferred to ones that are much better. At least in the pre-Darwinian economic version, I'd be interested in knowing how.