I have heard some pilots state that if you three point, you have the tailwheel on the surface to help you maintain directional control. I was never quite sure this was the case. Yesterday, I found more evidence to support my belief that the rudder is actually the much more effective means then the tailwheel. I have installed an MT reversing propeller on my taildragger. In getting used to it, I'm getting more comfortable applying lots of reverse thrust in the latter stage of the ground roll (airspeed and RPM sensors prevent application of reverse just after touchdown - as it should be.
What I found was that with the tailwheel nicely planted, the use of lots of reverse "stole" the airflow from the tail, and the rudder suddenly became very ineffective. Even though the tailwheel was nicely down, steering was very demanding at the moment the reverse had effect. I selected forward again, and the rudder was effective.
With this added insight, I further believe that it does not improve steering to have the tailwheel on the runway, if there is still enough airflow over the rudder to make it effective. I have found in all taildraggers I have flown, that if I have enough elevator available to hold the tailwheel off, I also have enough rudder control to steer.