Someone has to draw the shoes. Depending on who you ask, this is the easiest part or the hardest part of footwear development. The designer has to draw what people want on their feet.
To be a shoe designer, art school would be a great help. A degree in Industrial Design or Product design is a great place to start. But that said, if you can really draw like a bandit you may not need higher education. Designers draw the shoes and then work with the developers to make the prototypes just right. Picking color trends and knowing what is cool are critical skills.