Multiple parts to a header-only library can be concatenated into a single header file for easier inclusion, however. Some single header-only libraries are actua

Multiple parts to a header-only library can be concatenated into a single header file for easier inclusion, however. Some single header-only libraries are actually built this way. I agree with you in principle though. A directory of header files is, in practice, and in my experience, no more difficult to work with than a single header file and (can) allow for more modularity.