Because it does not target other endocrine glands. Tropic hormones regulate the secretory action of another endocrine organ, unlike non-trophic hormones act directly on the requisite organs. Growth hormones target tissues sush as bone, skeletal muscle, and etcetera. Examples of non-trophic hormones is vasopressin, oxytocin, testosterone. The Hypothalamic-pituitary-adrenal axis is a perfect example of a trophic hormone pathway.