If you have a personal account for clients or who users need to make actions before or after purchasing your service/product, then you need a training.
You may think that your product is simple, but that is not always obvious. Users can get confused about features, characteristics, what's better to choose and, eventually, leave. Also, training videos/articles/courses help to unload the technical support team, as they close many initial questions and increase customer loyalty to the brand securing the company status as an expert.