Because building muscle naturally forces you to get your diet right, figure out you natural metabolism, macros and forces you to understand and accept your genetics. You begin to learn what works and what doesn't therefore you have to put more strategic work in. You may find certain diets and strategies are worthless while others work amazingly for you. When you can truly maximize on your natural potential with diet, genetic potential, training and strategy and then choose to use gear the results will be ten fold. And you'll be all the wiser for it. Hands down the natural bulk and cut is the most ego destroying thing to go through but you learn in the process