> Most people watch television without knowing that the picture is comprised of pixels (or scan lines). Is that also sad?

That they don't know? A bit. That most don't want to know? Very, very sad.

> Why should my mum need to understand what an operating system is, let alone care about it?

To better be able to protect herself against malware, to be able to better understand a very important tool in our society, to be able to understand what your work is about when you tell her.