Why are the strings on paramotors so long?
The answer to this is mechanical leverage.

For this, you must understand that the center of mass for a paramotor is usually just above the pilot's head, and that the center of lift is more upwards.



The shorter the strings on a paramotor, the harder that it is to climb, because the length of the effort arm is reduced, requiring a greater power to tilt the paramotor into a climb.

As the motor power increases, you don't actually go much faster. You tip backward, and maintain speed. This is what helps you climb, essentially comboing the wing with the elevator.

The long strings allow for slower, more efficient flight by increasing leverage. This is the same mechanics that are used in most trainer crafts (outside the military) to allow the learner a long, slow flight.