"dpkg --add-architecture" not implemented in Ubuntu 12.04.1 LTS

According to "Multiarch/Implementation" on Debian Wiki
http://wiki.debian.org/Multiarch/Implementation

Ubuntu 12.04 LTS should use the command

sudo dpkg --add-architecture

to add foreign architectures .. if some user wants..

sudo dpkg --add-architecture i386

returns

dpkg: error: unknown option --add-architecture

Type dpkg --help for help about installing and deinstalling packages [*];
Use `dselect' or `aptitude' for user-friendly package management;
Type dpkg -Dhelp for a list of dpkg debug flag values;
Type dpkg --force-help for a list of forcing options;
Type dpkg-deb --help for help about manipulating *.deb files;

Options marked [*] produce a lot of output - pipe it through `less' or `more' !

So why this command not exist in dpkg in Ubuntu 12.04.1 LTS ?
I know that I can add a foreign architecture via /etc/dpkg/dpkg.cfg.d/multiarch
but just asking about the command..

Same question exist in Launcphad Answers Tracker :
https://answers.launchpad.net/ubuntu/+source/dpkg/+question/221647

Thanks

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: dpkg 1.16.1.2ubuntu7.1
ProcVersionSignature: Ubuntu 3.5.0-23.35~precise1-generic 3.5.7.2
Uname: Linux 3.5.0-23-generic x86_64
ApportVersion: 2.0.1-0ubuntu17.1
Architecture: amd64
Date: Tue Feb 12 14:47:53 2013
InstallationMedia: Ubuntu 12.04.1 LTS "Precise Pangolin" - Release amd64 (20120823.1)
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: dpkg
UpgradeStatus: No upgrade log present (probably fresh install)