I think you (and the author) give the average user too much credit. To most people on HN, it's probably pretty obvious that downloading applications directly from sketchy sources is a good way to have your device become infected by malware, but the average user might not realize this. They might not even realize that a source is sketchy.

This is anecdotal, but after about the 10th time reinstalling my parents OS, I finally discovered that the root of all their malware-related problems stemmed from the fact that they were downloading music using Limewire. It hadn't crossed their minds that perhaps this was not a very good idea.

I'm sure they genuinely believed that their computer was repeatedly being infected "through no fault of their own".