This is simply not true.
Average consumer purchases a Desktop from commercial retail store and it comes pre-installed with a version of Windows. This average consumer will not change the operating system for any reason. If it doesn't work, they'll call family tech-support. If it still can't be fixed, they'll take it in to a computer repair shop.
There isn't any compelling reason for a user of a pre-installed Windows computer to switch their operating system. The entire culture and market practically demands you have access to a Microsoft-operated PC, and Microsoft software.
Even if a linux distro had a completely identical UI, and it was binary compatible with Windows, what would be the point of switching operating systems (why go through all that work when it's exactly the same as what they already have)?
I run Linux on the desktop, have for over a decade. It's my primary OS, but you're just not going to get current Windows users to switch. The best chance Linux-as-desktop has of going mainstream is if Steam follows through with switching to Linux: http://www.tomshardware.com/news/Linux-Steam-Ubuntu-Native-Support,15444.html