I don't know - it's just a default general API, obviously it's not going to match everyone's use case. I would say that even relying on sort made by someone else is already not fit for many use cases.
If such a petty and trivial "problem" is what you have against Javascript, then you are basically saying it's a good language :--)
Why? Sorting strings is a far more common thing to do than just sorting numbers, so it makes sense to use simple string comparisons as the default algorithm. Rather than come up with something that first evaluates the types in the list and then tries to figure out what to do.
No, it makes sense to sort strings when you get handed strings, and sort numbers when handed numbers. Period. Default behavior is now exactly as expected by 100% of developers.
Your creativity as a language designer should only come in to play when dealing with sets of mixed type.
Both Python and Erlang would return [1,2,3,"a"], Ruby and Clojure won't allow the comparison. Either of these approaches makes more sense than JavaScript's.
