The Debian base system comes with both vim-tiny and nano. Nano is the default; when the installer wants you to edit something, you get nano:
$ ls -l ./etc/alternatives/editor
lrwxrwxrwx 1 root root 9 Sep 7 06:19 ./etc/alternatives/editor -> /bin/nano
If you want to use vim for development, use vim. But "it's the default" is simply an untrue statement. Vim (-full) is no more "the default" than Emacs. Both need to be manually installed on nearly every operating system.
(OpenBSD ships with both nvi and mg, FWIW.)
