It's hard to will a platform into existence without distribution for it. For all they knew at launch, iPhone would flop as many new products do. Adding platform

It's hard to will a platform into existence without distribution for it. For all they knew at launch, iPhone would flop as many new products do. Adding platform development into that risk directly hurt the chances of the product's success. But once it was evident that the product would succeed and could become the distribution mechanism for a platform, it made sense to open the internal SDK they already had for the built-in apps and turn it into a platform.