When a manufacturer grades a jacket down, sleeves, torso, and back length usually shrink slower than the chest and waist. A petite rider ends up swimming in sleeve while the jacket still pulls across the front, and the elbow armor sits halfway down her forearm. The same thing happens with trousers, where the knee armor lands on the shin and the inseam puddles at the ankle.
Misplaced armor is the real cost. Protection only works where the impact lands, so a pad that has slid past your elbow or knee is decoration. For a shorter rider, getting the proportions right is a safety decision, not a vanity one.