Several applications - eg cups, dbus and samba seem to have the trait of not wanting to create directories they need in order to be able to run. Later versions of cups appear to have dropped this "feature" but, as you point out, samba (and dbus) kept it.
I'd previously added a wrapper script to test for missing directories/conf files with cups and (maybe) samba, but I really don't know enough about samba to know the full range of directories/conf files that might be needed for its many uses.
Perhaps we can capture the various samba comments in this thread and I'll add them to the info file every now and again.
BTW, if you're working on an extension, please feel to say so in the forum so we avoid duplicating our efforts