ELF files have support for sections that are not loaded into the runtime
program image by the kernel.
Correct. The difficulties are social and not technical. The tools you would need to extract such things conveniently, elftar(1) or mount-elf (1) and accompanying libraries don't exist and probably wouldn't be much used, thus would tend to be buggy. On Windows, embedding resources for GUI apps into .EXE files is commonplace, but they are typically extracted only by Windows's own GUI libraries.