In Germany we have a saying, "Was der Bauer nicht kennt, frisst er nicht". Most people just don't care about operating systems, and hence they do not see the point in trying another system when the one they know works well enough for them.

A couple of years back, I set up my parents' notebook to dual boot either Windows 7 or Ubuntu 12.04. Despite the fact that both their printer and their (ancient) scanner worked out of the box (which did not work on Windows 7 at all), they have never used it.

On the other end of the spectrum you have young people who equally do not care about the operating system, but do not have such strong ties to Windows. I was amazed that when I gave my Ubuntu laptop to children on our family meetings, they had absolutely no problem using it for anything they needed. It was mostly just browsing the web and watching YouTube, but the point is that it was not alien to them. If more cheap laptops shipped with Ubuntu pre-installed, the adoption could go up significantly.

Until their school ask them to produce a document in MS Office, or they want to play a game that is not available on Linux.

I installed Elementary OS on my niece's computer because she lost her Windows licence. 2-3 weeks after that, she told me her computer was "broken". The reason was that she tried to run some apps (win32) but of course it didn't worked.

OpenOffice documents are compatible with MS Office (and I think OO can even save them in MS format, but I'm not sure of that.)

Changing habits is hard, most people don't want do it useless they are forced to.

5 of 6 years ago, my mother's old computer died. All the new ones where running Windows 7 while she was used to XP.

I seized the opportunity to install Linux on here computer instead of Windows 7, and she was OK with that because she was going to be in a new environment anyway. She is now a proud Linux user for 5 or 6 years :)

The only computer that runs windows in my house is my dual boot machine. My parents and my sister all have ubuntu distros, because 99% of the time they just need firefox and a text editor.