Each client connection is entirely independent of the other client connections. That's trivial to parallelize (thread pool, Erlang, whatever).
I also have one where the clients are almost entirely independent; that one connects to a database which handles the "almost" part.
But maybe you're someone who's happy with the cores and algorithms he already has. That's OK with me. There will certainly always be problems where shared-nothing parallelism over commodity hardware is the most cost effective. But not everyone is mining Bitcoin or computing the Mandelbrot set.