It had good early iterations (Knuth said once that he didn't even have to submit his suggestions for documentation, they turned up in the next version [1]). Kind of the opposite of JavaScript... [2]
As a multi-paradigm language they can add new functionality without having to replace old. The global namespace has thousands of functions, being able to add to that makes fixing problems more a matter of finding good names than a matter of finding "the right way" of doing something. E.g. Block and Module [3].
These are small advantages that perhaps most API and language designers don't have.