I am adding a tutorial to SewerJacks. I have a readme file, a hints file and online help via the '?' key, still people wonder why they die to a giant rat in the first level. Some games need tutorials some dont.
The big RLs should have them, because they are the ones that new players will generally experience first. If people do not understand something they will move one quickly, leaving the world of roguelikes behind, and continue playing something like Icy Tower. We need to capture the audience and hook them as quick as possible, a tutorial is just one answer.