There actually isn’t the same “constant tension” with the bands. people use the bands because they have an adjusting resistance. The farther away from the original point you get, the harder and “heavier” they feel. It works the same way as people putting chains on equipment. It is just a different way to shock the muscles. If you did them with cable, the weight would be evenly distributed the entire exercise. The bands seem to be more of a pump exercise used for higher reps that with the cables.