The things I did when I was a kid or young adult are things I would not consider doing as an adult—well, most of them anyway. I started my exploration of transportation equipment with a tricycle. Then, I graduated to bicycles, motorcycles, cars, trucks and forklifts. People mature. Our skills and competencies increase.
Similarly, the process of developing new products also goes through levels of maturity. We start with models, then move on to prototypes, advanced prototypes, and so on, until we reach the final design.