Why? The police officer gets paid the same either way. And that's probably in line with how we want it, lest police officers start seeing infractions that don't exist when their daughter's next birthday comes near.
That can help, but policy doesn't execute itself, it's executed through the police officers. Most cities aren't prepared to be able to follow-through to the logical conclusion the steps they'd need to take if their police force is fully intransigent with regard to following policy, so the policy itself is set based in part on what the force itself is willing to enforce.
Either I'm confused or maybe you didn't understand my point - why wouldn't the department want to execute a policy that benefits them greatly through increased revenue? If it's not profitable or desirable to do so, increase the fines.