What do you tell a new trainee in the case that he has been reading IT books as company documentation, and has a question with which he needs your assistance? He wonders why during troubleshooting and resolving issues, he needs to document everything.

You effectively establish a trail for other experts to follow when they experience similar situations by documenting the issue, the measures you did, and the resolution. In addition, if a similar situation arises, you may review the history to determine if there is a trend, or whether a new preventive step should be done (such as replacing equipment or going with a different vendor).