[throwaway125]

It's because the distinction isn't meaningful for day to day use. People use and compare languages and their standard libraries as a whole.

I do think people recognize the fact that these two are different things (e.g. when comparing C to a language with a richer standard library it's one of the points that are often specifically and separately mentioned.), but it's just not very useful to separate them explicitely in a comparison of languages from a user's point of view (as opposed to a language designer's point of view).