I realize that a lot of packages don't include licence files (e.g. glibc). I'd mistakenly assumed that was automated according to the "license" fields.
Also, some license fields aren't complete -- compare glibc's lgpl with the contents of Debian's libc6 "copyright" file, which includes gpl, bsd, and others, not just lgpl. Should bugs just be filed against each case, or can things be checked systematically? Related to that, licensecheck doesn't seem to be packaged. If it was, could it be used by "lint" (or something else)? I don't know whether lint is supposed only to process the package description or could look at the package contents the way Fedora's review tool does, for instance.