In over a quarter century of computer ownership, I've never had the misfortune to need to take a computer in for repair. Because of that, it never occurred to me that the repair person might be unscrupulous and pry into my private files. I'm glad that I have the skills to make sure that I don't need to risk my private data be viewed by a repair person.
A few years back, my sister asked me to fix her computer. In the course of testing her computer, I opened some of her doc files to test they could be read. When I gave her the computer back, she accused me of reading her private files!