Even if you typed that in by hand, you sure took a big detour on your journey of simply declaring "I just want the latest version of Scalatra that works so I can begin coding" by having to go specify Jetty version 7.6.0.v2012012759 and friends.
I don't find it "too difficult". Rather, it's just confusing, nontrivial, and it obstructed my progress with Scala.
*I know g8 just copies down a project from Github like https://github.com/scalatra/scalatra-sbt.g8/blob/master/src/..., but having tools that generate input for other build tools is along my point.