It's a lot harder to email paper? there aren't many good paper VCS? Paper is great for quick sketches and has its place. Digital is good for lots of other use cases. Maybe use what suits on a case by case basis?
I'd like to see a designer speak up about using stuff like this more than one time. I find I'd hard to believe that you would sit down, after already playing around with this once, and say "this time I'm going to add a chevron to each cell, put the button on the left side, and go test it in the hallway". If your app is a table with a stock navigation system do you really ever need to build a second version of the same thing?
Every project/team is different. Sometimes a designer wants to communicate with another designer, sometimes with a developer and sometimes with a client. Each of these stakeholders will react differently to:
'...this screen looks like.. well you know a stock tableview'
And sometimes these people aren't in the same room/building/country
Simply dismissing the tool because you cant think of a use-case is a bit short sighted.
PS: also when designing for the iphone, elements have a surprisingly different feel when shown on a device.