Why would it ever be besides the point to hit your target?
That's not what I meant.
Again, taking the limited example of somebody trying to cut or strike your wrist, a defensive move would involve proper use of the blade, body movement, a possible counter, and other factors. The tsuba might or might not be involved. My point is that while the tsuba might offer some protection, it's besides the point arguing that it should be there or not because it's not an all-defining factor in every situation (it depends on what you're trying to do). Besides, the other person also has a tsuba, so if it offers such a distinct "artificial" protective advantage as some claim here, wouldn't that make it a fair match?
I don't know Chiba's sword techniques so you'd have to go ask those who do why they're using tsuba. That said, the one example shown in the video is not the only way your wrist could be targeted. In many cases, the tsuba is not going to save you or help you much or at all.
If your wrist attack is completely compromised by your opponent having a sword with a tsuba... what kind of sword training is that? It shouldn't matter. Any proper style or technique would consider the presence or absence of tsuba from the onset; so again, it's besides the point arguing that it should be there or not.