This is a simple case of specialization of labor. While a hacker may be able to hear the voice of the customer, it probably makes sense to have some folks that

This is a simple case of specialization of labor. While a hacker may be able to hear the voice of the customer, it probably makes sense to have some folks that do more hacking and some more customer hearing. If you have two co-founders, it makes sense to have one on each side.