By that I mean, just one for instance, all dogs can bite. However, some dogs bite less well. While it may not matter in your style, and maybe you can overcome a lot with emotion-based training. However, I would be interested in seeing how a dog in your style would deal with issues if it bit shallowly (which is not just a sport thing, it's easier to shake a dog with a crappy grip and I have gotten the impression it's easier to break a tooth with a shallow grip if it's just the canines and not a fairly full-grip), or had issues in training biting certain materials. Plus, by doing it over time, the dog should be more confident and just get better. That's sort of the rationale behind sparring and ramping up to train before a fight (whether you're Jon Jones training for an MMA fight, a citizen training in Krav Maga for self-defense, or Charles Bronson [the prisoner, not the actor] developing a workout program basically for street fighting).
I realize you are training in a way that is sort of outside the norms for most here. However, if we open it up to a more general training discussion I would like to think this is a valid question.
Purely as a Devil's advocate argument, if you train without any equipment the question I know most would have is, unless you actually train and test your dog in biting, how would you know they will do it or how they will react in the moment? What I suspect most any sport, Police, security, personal protection, or other equipment-based trainer will say (and correct me if I am wrong) is their training best simulates what happens in an actual encounter. Yes, they start out with a toy or huge sleeve. However, just like hitting the heavy bag that does at least somewhat translate some skills into an encounter with a real live person. They likely just work toward hidden sleeve a/o muzzle work. Anyway, most would probably ask if you do not actually do it (with "it" being as close to a live bite or scenario where the dog believes it is as real as possible, and presumably uses their mouth in a manner they would in a real life scenario), how can you really know for sure how the dog will act?
E-Dog - 2012 WPBTCA National Championships
The time when screech owls and Bandogges howl and spirits walk and ghosts break up their graves.
Act I, Scene IV of William Shakespeare's "King Henry VI"