He is not saying that the skills required to build the product are not necessary, he is just saying they are not sufficient. You need to be able to build the p

He is not saying that the skills required to build the product are not necessary, he is just saying they are not sufficient. You need to be able to build the product, AND have people to sell it to. Having people to sell it to first helps you build the right product in the first place. In the supermodel example, you might still need to go to the gym and buy a flashier car, but you won't know that until you actually start meeting supermodels and talking to them.