You would not buy an operation system that would not let you use your computer when not online
I don't know much about it, but isn't that the basis of Google's Chrome OS?
I agree with this and add the fact that some of us with young children don't really want them to see some of the violence in the games we like to play. I don't really want my young children to go to bed while visions of splicers dance in their heads.
Any sufficiently advanced technology is indistinguishable from a rigged demo.