I can't speak for its author(s) but the point of vimtutor is to help you learn Vim's basics in order to be up and running as quickly as possible. From that point of view, it's quite normal to go without special settings and plugins as that would taint the whole experience and learning. Vimtutor is a standardized tool and it would probably loose a lot if it was different for everybody.

By the way, going config-less for two or three days can be an eye opening adventure if you are too infatuated with your config.

Also, what would be the point of running vimtutor if you already have a ~/.vimrc? You probably already know everything it has to offer.