About a year ago I was "asked" (being the allocated family nerd) to get rid of some m$.viruses.m$ and "it stopped working" type nagging.
As I was told all backups were done (thankfully I taught them about that) I just installed Linux on my Mothers and my Sisters pc's.
So, a year or so later after no crashes, viruses and an apparent abundance of magically free software they asked me what Linux was! I was delighted to tell them they have been using it for around a year.
At first I had Ubuntu but have settled on Fedora 8.
If they were asked today what a "cli" or even an "os" was, I'm sure they couldn't tell me. They're not stupid, it's just not their forte.
So, in my opinion "the average user" just doesn't care or more to the point doesn't even know.