Actually, it has little to do with torque wrenches.

The torx fastener's primary reason for bieng is mass production. On the assembly line, it might be your job to install 240 threaded fasteners per hour. If you try to put a phillips screw on a power driver (electric or pneumatic), chances are pretty good, even with a magnetic bit, that it won't line up with the threads into which it is being inserted. A torx will. They stay on the bit better, therefore an assembly worker can install more fasteners correctly per hour.

And the advantage over Allen/Internal Hex is that it is easier to get onto the driving bit.

The consipracy theorists said, when the torx first came out, that the reason was that the manufacturers didn't want you working on your car. At that time, Torx drivers were not readily available. Not true today, so that blows that theory out of the water.