I think they should: they are very useful to introspect the model behavior as documented as such in the [narrative documentation](http://scikit-learn.org/dev/modules/feature_extraction.html#common-vectorizer-usage). I often point to them to user who want to understand what the vectorizer is doing on stackoverflow, for instance:

http://stackoverflow.com/questions/16080726/special-characters-in-countvectorizer-scikit-learn/16083182#16083182