Extensiosn are not just for academia. If I am building a microcontroller to control the storage media I am selling (eg. hard drives), why do I need to implement

Extensiosn are not just for academia. If I am building a microcontroller to control the storage media I am selling (eg. hard drives), why do I need to implement a bunch of features I am not going to use? What about my flow rate monitor? Or my pacemaker? In some of these, less silicon means less power means more better. Like that last example.