Touch screens are to desktops as push bikes are to tractors. You need both. Some people even use both. Or just one. Or neither.
Maybe you feel this way because you've been driving a tractor around all this time and you feel like you've been wasting your time, however some of us (I imagine a lot of us on HN) like to do farming occasionally :-)
"If I had asked people what they wanted, they would have said faster horses."
http://blogs.hbr.org/cs/2011/08/henry_ford_never_said_the_fa...
You say that nobody wants to use desktops and people want computers to disappear. Unlike you, I don't believe that already, so do you have some evidence for it?
Took my old brain a second or two to realize that I had previously heard that quote associated with Henry Ford.
However, we still use horses as transport. Sure, it's often just for pleasure, but the Police still use them, and rural people still use them, or people in mountains etc, because in those situations they are still better than anything Ford came up with.
So I don't think that quote is relevant here. People have accepted 'post-pcs' into their lives and they are good at lots of things. There are things that larger 'real' computers are better at though, and I don't see any evidence that will change.