It bothers me too.

Dynamically typed does not imply no types. A good CL implementation takes that to heart and produces really nice code out of the box. And the language spec provides for an API to allow program developers to specify types and hints to the compiler to optimize certain functions and code paths where it's needed.

The benefit from this is that you can rapidly prototype your application and harden it to the platform you deploy on when performance becomes an issue... and with built-in conditional compilation you can do that in a cross-platform way.