That's just not really true though. There are other ingredients in box mixes, such as conditioners and other incremental improvements grandma doesn't have a container of on her counter. You certainly have more control over the final product if you mix everything from scratch, but these mixes are popular for a reason; they make good cake without having to reinvent decades of kitchen science and allow bakers to focus on stuff that matters instead of dick-measuring about who can sift and measure flour the best.