I'd go further and say that most users don't understand the difference between OS, hardware and form factor\case and see a computer as an all in one appliance n

I'd go further and say that most users don't understand the difference between OS, hardware and form factor\case and see a computer as an all in one appliance no different from a smartphone or a console. You can see this when people talk "Mac vs. PC", they'll talk about the features of the hardware and the OS interchangeably (Macs are better because they get less viruses), even though bootcamp has been an officially supported path on Mac hardware for a long time. There is a marketing problem with mainstream users in that most people don't know what Linux is, but I'd guess that many people don't know what Windows is, probably don't know what Android is and don't know what iOS or OSX are, so I'm not sure if understanding what Linux or Ubuntu is actually matters for usage. I completely agree in that sense that Linux would work for average desktop users if OEM's installed it. The only major barriers I can think of are lack of MS Office and potential support overhead. Companies would have to hire a lot more dedicated Linux desktop support staff.