They are not shown in
help because they are not defined in any one place.
The commands shown in
help are known as "built-ins" (i.e., "built-in commands"). They are provided by the shell (
cmd.exe), and are just internal functions. Everything else is an external program which is executed and run with the arguments provided.
These programs can be anywhere in your
%PATH% is a system variable which contains a listing of paths to search for programs that can be run. It's basically just a list of folders.
When you run
ping X.X.X.X, it starts looking through them until it finds a folder with a file called
ping.exe and tries to run it with
X.X.X.X as the first parameter. (Hint, I think
ping.exe is in
C:\Windows\System32, where most of the utilities that you listed live)
Why doesn't it list all the possible programs? Because there could be thousands, and enumerating all of them could take a very, very long time (and the purpose of
help is to list the built-ins, so you know which commands are provided by the shell and should be available on any Windows system and which are not and might be missing or different on a particular Windows system).
Upon deeper investigation, there seems to be a few commands listed in
help which are external commands (like
icacls). I can only speculate on why they were chosen for inclusion, but the above still holds as a general rule for shells (be they for Windows, Linux, or OS X), and 90%+ of the commands listed by