Why is 'ppa-purge' not installed by default?

A lot of websites encourage you (OMG Ubuntu...) to install ppa's but doesn't tell you how to uninstall it. On a default install it's possible to install a ppa by a one-liner but uninstalling isn't a one-liner...

Second: The names of the apt cmd's are strange -> 'apt-add-repository' and 'ppa-purge'. Why not 'apt-add-repository' and 'apt-purge-repository'??? (create an alias could help)

If I'm right, precise will have a 750 MB iso, so they should deffinitly add 'ppa-purge' to the default disc.

Is there a dev that could explain me why 'ppa-purge' is not installed on default Ubuntu 12.04?

Software that is included by default on the CD/ISO is generally expected to be useful to normal users doing normal use cases.

Generally PPA's are meant for development and testing, not regular end user consumption as there's never a guarantee that anything in a PPA is tested and working:

• Are PPA's safe to add to my system and what are some "red flags" to watch out for?

If a user is using a PPA then the extra step of adding ppa purge isn't really that much more effort as that person should already understand the risks of using PPAs; that and it's easy to find in the archive already. Sort of like how we don't ship a compiler by default; the people who know they need it know how to install it already.

add-apt-repository can remove a repository with the -r switch, but all this does is remove the repository, it doesn't roll back the packages to the prior version like ppapurge does.

That being said, I've not seen anyone ask for ppa purge to be installed by default as it is. As far as adding an alias, you should file a bug about that.