People do, but most problems can still be solved just as easily by the standard set of programmer tools. Most desktop apps don't need to scale across multiple

People do, but most problems can still be solved just as easily by the standard set of programmer tools. Most desktop apps don't need to scale across multiple processors (yet) and most web services can get by without needing serious scaling muscle. Some of this is starting to change, which is why languages like Erlang are being noticed and talked about (and even used) at the bleeding-edge. Revisit this question in four or five years and the question will probably be more along the lines of "why are people still using <insert current popular language here>?"