It's super cheap, making it more appealing than some other gyms, but once you get in you find out why: you're not supposed to actually use any of the equipment.  It's for fat people who go in and "exercise" once a week by doing some walking on a treadmill, or a couple reps with weights.  If you actually use the equpiment like you would at a real gym, it'd put too much wear and tear on the equipment and Planet Fitness would have to spend more to replace it (like any real gym).  Their entire business model is based on people paying a small amount and not using the equipment, giving them decent profits. They also have things like "free pizza day".