I think the punishment should reflect the crime.
If fines and or punishments are used primarily as a deterrent, then why not just have huge punishments all over the place?
Do you see how that's immoral? Fines should be used as punishment, not deterrence (punishment is a form of deterrence, but is merely a side effect). If I decide to litter, it's because I think "this is not that big of a crime. I'm not harming people very much." It's not anyones natural moral instinct to think, "I would do this, but the penalty is to high" - we're conditioned to think that. But as is all to often, a lot of times people are not even aware that their actions may be illegal, or may not be aware the consequences are vastly harsher than the crime. Do you know what the penalty is for driving with one bad headlight? me neither. I hope its reasonable, especially when I make the decision to do it, but I base the decision off the fact that driving without a headlight does not seem that egregious of a crime.
So shouldn't our punishment system be base off the same thing that people use to guide their decisions? The results of our actions?
The answer is yes. I don't want to live in the world you are imagining. Even if there is no litter on the ground and no one speeds.
If you say, just inform everyone of the laws really really well so they know beforehand when making a decision, that is utterly impossible. Foreigners exist. People are busy. All laws are not even totally known to the lawmakers. It is an impossible task.
Back to your point: If the goal was to stop speeding, they would make it physically impossible to speed. Either by really pervasive robotic enforcement, or governors in cars. But they don't do that, they want the money.
Still, the punishment should reflect the crime, even in the robotic police world.