Some gliders have very poor roll control at low speeds, and an aerotow takes time to accelerate to where it's adequate.
Yes, I see that, but in what way do the airbrakes help with low speed roll control? I would have imagined that, if anything, the additional drag would contribute to the slow acceleration, but maybe I'm being dim......
Afterthought.......perhaps gliders now have differential airbrakes/lift dumpers that would provide some roll control, and I'm just 30 years behind the curve.....?