I disagree. State machines are used in many fields, not just in software that evaluates data. As a tiny selection of applications, they are used to drive washing machines and dishwashers, as well as most battery-driven toys. In those cases, they certainly don't parse anything, but simply perform timed steps of a program to wash your dishes or clothes (I hope they are not being parsed!), or move a toy car while making some fitting noises. Similarly, in software, they are used in practically all programs in one form or another. Just think of any game you know, and it certainly is based on a state machine.