Aileron Torque Rods
Torque wires on sport models work nicely as the ailerons are strip-type and extend all the way to the fuselage. Scale planes have barndoor ailerons and it would add a lot of weight to run a rigid torque wire plus its support bearing all the way to the tip. Much simpler to use two servos with direct linkage it seems to me. Also, the use of more than servo allows for other functions such as aileron differential and elevons.
Dave Segal