Also, compiler design classes are not obscure. Mine helped me land a job... working on a compiler. Additionally, I find state machines in many business domains

Also, compiler design classes are not obscure. Mine helped me land a job... working on a compiler. Additionally, I find state machines in many business domains. Everything that some kind of "ticket" object (be it customer support or defect tracking) will (or should!) have state machines, with rules of varying complexity, to escalate the status of these tickets.