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.)

I'm pretty sure its vim-tiny

Please substitute "vi" in my comments for "vi or appropriate compatible substitute" such as nvi, vim, elvis etc. They all work the same with the usual subset of commands :)