I cannot speak highly enough of the Technical Writing courses that I took in college. These have been the most useful courses that I have taken regarding application. It has applied to nearly every role has made massive differences in every environment.
Solid documentation has the ability to dramatically cut down on the amount of time to train others on a variety of tasks; time that would otherwise by required of other people. Not that documentation can necessarily replace one-on-one interaction for training. Having a solid piece of documentation can cut days to hours, hours to minutes.
Years back, I was on a string of contract jobs doing full system replacements for hotels (PC's and Servers). The IBM contact showed up with a massive binder of documentation that outlined the entire process. I asked him how long he'd been doing it to which he replied "30 years," and then I asked him if he actually needed the documentation. He chuckled at me and said, "nobody is perfect." He went on to say that though he could do it blindfolded, it wasn't worth the ego boost to potentially miss a step.
On the same contract string, he wound up sick and didn't make it to a site. But we had his binder of documentation that he had left with the front desk. We were able to accomplish the job without him because his documentation was so bountiful and precise.
That is how critical a good set of documentation is. If it is written at a sixth grade level, written as though English is your second language and it includes every step, then it is possible to let anyone complete the work.
The validation process is just as critical. A piece of technical documentation is useless if it doesn't work. It needs edited, updated, and clarified in order to insure that no mistakes occur.