One leaf out of a whole tree.
I know most people can't be bothered but what about using the information to prune library bloat. For example, suppose my Hello World application uses some date library which uses some internationalisation library which uses some foo and some bar. Except that my HW only actually uses one API call from the date library which only uses one API call from the internationalisation library. No matter, there are 100 extra routines lurking in my code. So surely I'd want to spend a Friday afternoon cutting out the tiny bit I do need, or rewriting etc. to avoid the date library overhead. Then I have a much more manageable development environment with fewer risks of being struck by a wild issue from out of the Wide Blue Yonder. (Plus other benefits.) Perhaps somebody could invent an 'optimising compiler' for or 'standard library internal dependency map reader/writer'.