Not sure about the charts themselves, but it helps structure code and logic better if a clear description of possible states (of phenomena) is provided and reasoned about.

Naturally, as the author notes, we are using states in our programs. Three kinds at least

- current program state in the complex space-of-states the program can have - most properties (and vars) are expect to undergo several states, and enumerable denotes a state. - every program traversing a graph for something, essentially runs a state machine of some sort

Indeed a user interface can benefit from having a FSM run it, given interfaces guide the end-user through predefined states from which he navigates into other states (which show/hide a set of widgets and wire them with data).