I have seen state machines quite frequently in production code, but rarely formally defined state machines. For example something I've seen a few times is a db

I have seen state machines quite frequently in production code, but rarely formally defined state machines. For example something I've seen a few times is a db table with the fields "account confirmed bool" "account_deleted bool" and "account_suspended bool." There's a state machine in that app somewhere, even if they wouldn't describe it that way. I think developers having better awareness of when they're drifting into this approach and intentionally choosing it or not would be a much better situation.