The only thing I'd add is that there exists a report on the wrongful conviction of James Driskell. One of the things the Crown did in that case was to prefer a direct indictment; they skipped over the preliminary inquiry. Thirteen years later, after James served all of those years in jail for something he didn't do, Justice Patrick LeSage looked into the wrongful conviction and concluded that the absence of a preliminary inquiry in that particular case, and the failure to discover the non-disclosure that led in part to the wrongful conviction, were contributing factors.
Again, whether we're talking about 5%, 10%, or 3%, for any one person who is wrongfully convicted, we want to do what we can to ensure a fair and just system. A preliminary inquiry helps achieve that.