Do you remember when your parents, friends or co-workers told you to lift with your legs when you lift heavy household objects?
Using the lower back extension machine is the equivalent of lifting a heavy object with your lower back only and not bending your legs.
When you lift a heavy object at home such as a TV, the correct way to lift would help functionally strengthen your lower back such as performing a dead lift with proper form.
The motion provided by the lower back extension machine is totally unnatural and can even lead to injury if performed incorrectly.