I was wondering the same thing. The "screwdriver" part of your Little Tarheel antenna tunes the antenna to resonance just fine. That's the whole idea of the antenna's design. No tuner needed.
The Turbo Tunder device, isn't an antenna tuner per se. It's more of a controller that winds the screwdriver up and down finding the best match per band. As you tune up and down a particular band, the device will retune the antenna for the operator.
I think Alan was asking why the Turbo Tuner brand, as there is at leat one other brand that does essentially the same thing and does it perhaps a little better obtaining +12V for powering the antenna motor directly from the vehicle instead of thru the rather thin foil trace on the PC board of the particular radio you're using. This is why I use the Better RF brand.