Probably because when somebody is using Linux, odds are good they're running Ubuntu (according to distro watch, for example). Ubuntu is as good as any other distro, and Canonical is making a remarkable work making the adoption of Linux work. Please, don't ruin that with elitist comments.

I'd like to see the day where the EU will do the same for Microsoft. I would like to see the day where I could buy a computer and either a) didn't have any OS installed (meaning I'd have to buy a Windows license if I wanted to buy it with windows) b) Force stores to give me the cashback if it came with a Windows OS and I didn't want to use it

Not true. I seem to remember XP was probably faster on my old PC than the Ubuntu version I used then (Feisty, if I'm not mistaken).