Most consumers can be clueless, attention deficient, instant-gratification seeking, work/knowledge averse ... or can just want something simple.
A lot don't even understand the concept of the file-system (let alone the other 95% of Windows).
A lot can't even download a picture from a camera's memory card and place it into the proper folder after you show them how to do it 12 times over 3 months.
And most can't be expected to do anything that requires more than 1 or 2 easy steps (whether they can but don't want to, or just can't).
Metro re-invents the way the average consumer experiences and works with Windows to the point that even the village idiot could do something useful with this OS.
Why do you think the iPad was such a success, and where do you think 95% of its users are coming from?! The dusty PC running Windows.
With Metor, Microsoft will keep dominating the home desktop market (as they do now), prevent the outflow of users, and introduce themself in a very serious way in the tablet and phone market.