The question should probably be what you gain from the header files? If you just want the simplicity you can "#include \"some_file.c\"" instead. Functionally it's no different, but it's less surprising to other people and it's an easier transition to a real build system if/when you need it. I think the reason it's being raised is because people think your writing a header only library.
In my experience, including `"some_file.h"` is more common than `"some_file.c"`. I also like knowing at a quick glance what the entry point/main file is. That's less explicit when all the files have the same extension.
