Reasons Linux isn't taking over the world
1) Things don't "just work" - why can't I get HDMI audio passthrough on my HD6450? Windows can do it, why can't Linux? I know, proprietary drivers.... but I'm the end user, that's not my problem: I just want to plug HDMI into things and have them work.
2) WiFi. Seriously, this isn't new, and there aren't that many chips out there. I should not still be having issues with a commonplace WiFi dongle. I know this is sort of related to the above, but it's a much bigger single issue: HDMI passthrough affects a handful of people. HDMI affects nearly all.
3) The command line. I'm pretty technical, I don't mind having a go in the command line... but there's a reason GUIs were invented and are so popular. Stop making me input commands to a black and white terminal. Webmin goes a long way to fixing this, and there are various other GUI's and tools for this sort of thing... but I still end up in Terminal far too often. I can handle it, my mum can't.
Plus points since I first dabbled with Linux probably 10 years ago:
+ Installation is easy. Put the ISO on a disk, plug it in, follow an installer which isn't much (/any) more technical than the Windows one
+ App stores. I always loved apt, yum etc on Linux, for grabbing tools it was great. Having package managers over the top of this works perfectly. Nearly. And is the basis of the App Stores on everything these days
+ Less interaction needed, it does a lot more than it used to, automatically
1 and 2 are both entirely the fault of the hardware vendors. The linux support is god-awful. Imagine windows drivers being built by people in their spare time with no access to the inner workings of the hardware. How well would wi-fi or HDMI audio work then?
What does your mum use that needs the terminal? You can install the OS, web browser, chat client email client all without the terminal and she never need see it.