Before anyone works in a trial system, they need training, and you need to be able to prove it. That means identifying every user across sites, CROs, AROs, vendors, committees and sponsors, then tracking what training each one completed and when. Turnover never stops, and re-training is needed if you modify your configuration, so the list is never finished.
Without a central place to collect and report on system user training records, there is no reliable way to produce complete evidence. Gaps surface during an audit or inspection, when it is too late to close them.