There are several reasons for not documenting information.
If the course of action or sequence of steps cannot be predicted a procedure or plan cannot be written for unforeseen events.
If there is no effect on performance by allowing freedom of action or decision, there is no mandate to prescribe the methods to be employed.
If it cannot be foreseen that any person might need to take action or make a decision using information from a process, there is no mandate to require the results to be recorded. (However you need to look beyond your own organization for such reasons if demonstrating due diligence in a product liability suit requires access to evidence)
If the action or decision is intuitive or spontaneous, no manner of documentation will ensure a better performance.
If the action or decision needs to be habitual, documentation will be beneficial only in enabling the individual reach a level of competence.