Usually, packages are removed from the default installation due to space constraint. CDs are limited ( and so does DVD ), and there is pressure to add more translations, to support more hardware ( especially with big binary blobs like the Nvidia driver ), etc.

So usually, packagers take a look at what can be safely removed ( ie, without removing important use case of a default distribution ). In the case of vim, there is already gedit and nano to fill the position and I would say that people who use vim are able to install it from the archive without much problem.