Camera tickets are in a weird place legally. They might not be legal, because of the 6th ammendment and due process requirements, so states tread lightly. A light touch gets a lot of compliance and is most likely self-funding; enforcement by humans may be more effective for habitual violators, but you most likely can't have as much coverage and be self-funding.

If you had 30 speeding tickets issued in person, it would be a lot different than 30 speeding tickets issued by machine.