Just because the source for a program is available, you should not use it unless there is an actual need. The rmail program, for example, is needed only if you have UUCP connections, and should not be used otherwise. The mail.local program is another that should be built and installed only on systems that support it. If you install and use mail.local on an unsupported system, you risk lost email.
Just because we did not describe the programs in the contrib directory, it does not mean we are critical of them. They have been omitted simply because they are not built and installed with the Build program.