I have to agree with @unman for the most part.
Of course, we’d have to define the average user and their abilities. For the sake of argument let’s assume the average user has grown up with using Windows, like myself.
I’ve just read an article on Microsoft closing large numbers of accounts apparently at random and people couldn’t access data (Onedrive, Office 365) and other Mircosoft services anymore. Disregarding the fact that one could learn and backup data in the future another point came up in the discussion that followed the article: move away from Microsoft and try out a Linux distribution or at least try out open source & free software alternatives to Microsoft (the basic stuff like firefox, thunderbird, libre office etc.) on Windows.
The discussion quickly fell back into the old patterns of Windows vs Linux which is so boring because many people don’t seem open anymore for a discussion free from any bias, exchanging arguments that are based on real experiences and trying to listen to well-founded opinions. Instead there were those who claimed that “Linux” (yes, they weren’t able to name a distribution) wasn’t usable because it was too difficult to install and it wouldn’t work and anyhow everything was better on Windows anyway.
I don’t want to go into details - there hardly were any. My point is that I think that in large parts of affluent societies people have become lazy and impatient when it comes to most things technical like computers, smart phones etc. In our throwaway society it is easier to dispose of something that doesn’t work like it used to anymore instead of investigating and trying to repair it or learn something new that could help making something useful again.
I don’t think that it is too hard to install almost any Linux distribution not to mention Qubes. Of course, you’d need to consult some basic stuff like Hardware Compatibility List and other documentation.
Most people don’t know much about or just don’t care about security and privacy in general and that is why they won’t use Linux or any other system than the one they are offered while shopping. It doesn’t matter what happens in the background as long as the stuff works.
I guess, the few people who really need a special kind of security because maybe even their lives depend on it will take the time and read a few pages of documentation in order to achieve that and at least ask some questions in a forum should need be. Wouldn’t you?