people do not use a computer to use it's desktop, they use the computer to get things done (either to play games, access the web, e-mail, write documents, watch video, etc)
a desktop either makes this easy or makes this hard depending on how it gets in the way of the user or assists the user.
Far too many desktop developers seem to think that the Desktop Environment is the end purpose of the computer, rather than just a means to get other stuff done.