Imagine if a user optionally could compile ffmpeg with only the code that the user will actually need. For example, a user might only use one or a few formats in practice and only a handful of commands for a limited number of tasks. Configure scripts often allow users to accomplish this to some extent, e.g., excluding libraries we know we'll never use. Another idea is that ffmpeg could output C source code that would assist with compiling a "single purpose" executable. Something similar to tcpdump -dd or curl --libcurl. (How many folks actually use those options, not sure, but they still exist.)

It's common to see comments from ffmpeg users where they have devised some certain command line that accomplishes some specific task but who otherwise do not routinely use ffmpeg for much else. If these folks were able to compile an application that performed only this task using only the required ffmpeg libraries, would this be smaller and less complicated than an ffmpeg static binary.