The existence of another language that creates faster programs doesn't make the task of optimizing software written in the slower language irrelevant.

Make sense? :)

And, I mean, languages like Erlang make writing software to solve certain classes of problems far easier than if one were using straight C. What's more, Erlang lets you plug in code written in other languages, so you can keep the very logically tricky stuff in Erlang, and do the perf-critical stuff in -say- C.