What you do is determined by physical action of neurons. There is no need for there to be someone to perceive it.

The need arises when you consider the complex social systems humans leverage for survival — our ability to navigate interpersonal conflicts and engage in cooperation relies on theory of mind and our tendency to perceive ourselves as individual free agents empathizing with separate free agents.

By definition, internal experience is something you perceive, and what you perceive informs how you act. Therefore internal experience affects outward physical action.