Weighing scales score on the fact that no experts are required for reading them—they are cheap, non-invasive, offer an instant result and are readily available, even if they score very poorly on both validity and reliability. Your weight cannot tell you if you have gotten more or less flexible in your hips, if your resting heart-rate has slowed down, or if your blood sugars are behaving better. You could have worked out diligently in the gym and improved on all fitness parameters—flexibility, cardio-respiration, endurance, strength, etc; you are even feeling lighter and better, but if that scale says no change or a gain of 2 kg (highly possible, as you make gains in lean mass and bone mineral density), your world comes crashing down! From enjoying the benefits of exercise, you needlessly reduce yourself to a number on the scale.