I think you pretty much summed it up in the first point: “People don’t like too much change.” When people see the ads demoing Windows 8, they compare it to their experience with 7 or Vista, etc, and conclude “that ain’t Windows!”

Interestingly though, I hear a lot of people who felt the same way but when they made a full transition to the new OS, they found that it was actually quite nice.

So, it could ultimately come down to a marketing challenge for Microsoft.