Turbulent flow would increase the overall drag in this situation. You're essentially taking energy from the free-flowing middle of the pipe and using it to drag

Turbulent flow would increase the overall drag in this situation. You're essentially taking energy from the free-flowing middle of the pipe and using it to drag more air along the wall. The reason why turbulence helps a golf ball is because it decreases flow separation http://en.wikipedia.org/wiki/Flow_separation http://en.wikipedia.org/wiki/Flow_separation. Separated flow makes a ridiculous amount of drag, and it's worth the extra skin drag to keep the flow attached.