Depends on the language and the platform. For instance, it is quite trivial for me to use a variety of databases while working with C, I just use the appropriate library.

A language must maintain its standard implementation, and that typically means providing the minimum amount needed for someone to be able to build whatever they want to build. Everything else becomes a library, or perhaps an extension to the language that is maintained by others.

At least, this is the case for languages that follow standards established by organizations such as ISO.