Several OEM's do just that, but nobody is buying.
> Notice that nobody has a problem with Linux on their phone, because it comes pre-installed.
No, nobody has a problem with these because Android has a good UI on top of Linux. Desktop Linux never came close to achieving that goal, hence its repeated failure to break into the mainstream.
Who? Dell has one 11" Ubuntu laptop on their website, and you have to try really hard to find it. System 76 has no marketing budget whatsoever. Anybody else? Have you ever seen a Linux machine in stores? Ever?
And the Android UI is okay for a phone, but I greatly prefer Awesome on my laptop. Mint, in my experience, has been really great for newbies. I just don't buy the UI argument. Windows baffles all the newbies I know. The "UI" problems with Linux have to do with driver support, and lack of a few big name pieces of software, that's about it.
Well, that and way too much choice. There's no "Linux UI", unless you're talking about bash or something. There's Gnome, KDE, etc. But one or a few OEMs settling on a standard desktop environment would go a long way towards standardizing the user experience, while still allowing us nerds to geek out on different window managers.