If people are explicitly told they can skip the tutorial, most will and it won't help player retention either. The tutorial reaches a compromise by leaving it up to the player by how its structured: we must choose to start the next chapter, we see Ozan specifically mention going to Draynor during the opening sequence, we're taught about world map usage, etc. It's set up to allow the player to explore or stick with an on-rails tutorial using the trail system.