While I subscribe to a lot of that school of thought (i.e. I love learning to work on stuff and being able to do things myself) there are two flaws. One, time. I know how to do a whole lot of stuff, but the time it takes me to do it can often be better spent elsewhere. I know how to mow my yard just fine for instance, but it is nothing more than a chore in my eyes hence why I pay someone to do that for me. Another example is I have firesticks throughout my house with, we will say special software, loaded onto them. I can easily do that work myself if I were so inclined, but I paid a friend to do it for me because he already had everything set up to do it quickly and cheaply. It is absolute insanity to try and do all of that work yourself because then you never have time for anything EXCEPT work.
Two, the entire point of our economy currently is specialization and selling services/products that are supposed to be better than what a person gets on their own/at home. I can do pretty good carpentry work, and do on the regular because it saves me money in the long run. I actually enjoy cooking a lot, and can make some fairly superb meals (or at least I'm told). That does not mean that I will produce the quality of work that Nick Offerman or Gordon Ramsay can do in their respective fields. Sometimes, it makes more sense to have someone else do it who is more highly skilled than you are at that job.
Not to mention, if I am not planning to do something repeatedly and don't just have an interest in learning it, it would save time and probably money to just pay for it from a professional. For instance, I can work on my own car and do from time to time if the fixes or maintenance is not overly time consuming (thermostat replacement, air filter changes, etc.). However, I do not own many of the more advanced automotive specific tools that would cost a lot of money and time to learn so certain repairs like replacing my catalytic converter I took to my trusted mechanic.
Same principle applies here, many of these people might even be able to figure out how to work on their own computer (Google/DuckDuckGo is quite valuable), but they don't have the time to learn something they are not going to do on the regular. Even those that do know how, they may not have the tools to do so effectively/legally and it is perfectly reasonable that they expect an entity such as Office Depot could provide at least basic service and not be essentially running a large scale phone scam.