You’ve just a conceded that enforcing said laws don’t actually prevent the crime

Except I didn’t concede that? I said enforcing laws doesn’t totally eliminate crime, in the same way that putting a soda in the fridge doesn’t drop the temperature to 0K. Enforcing laws reduces crime.

I would say enforcement never prevents any crime

I would say you’re demonstrably incorrect.

and enforcement is about punishment not prevention.

Punishment is the method of prevention. Additionally, incarceration is in part about removing law breakers from polite society so they do not continue to break laws. We quarantine the murderers so they don’t keep murdering people.

So when is it worth it?

As with most things in life, we decide on a reasonable compromise. Putting a soda in the fridge is beneficial, putting it in the freezer is too much, and causes more problems than it solves. We decide these things collectively as a society, by electing representatives to draft laws. When they overstep, we elect new representatives to change the laws.

How much abuse and Injustice is necessary to assuage your fears about the other?

What’s abusive and unjust about trying to prevent murderers? Where’s the justice for victims and their families if as a society we just say “Golly, sorry this guy killed your children, but if we punished him we’d be just as bad”? How do you recommend reducing the injustices people enact against each other?

Surely you’re not going to sit here and tell me only fear of punishment is what stops you from murdering people?

Me personally? Of course not. But obviously some people want to do crimes. You can’t build a society based on everyone behaving just like you all the time. Some people are more violent, or greedy, or deceptive. We are barely domesticated apes, jungle impulses course through us all. Some more than others. Without some mechanism to curtail that, consequences that outweigh the benefits of selfish behavior, you wind up back at might-makes-right anyway when the selfish behave selfishly with no recourse.

That doesn’t prove that not enforcing them would somehow make murder disappear, it just proves that you can’t absolutely eliminate a behavior. Every action has diminishing returns.

I can remove some of the heat from an object by putting it in the fridge. I can remove more by putting it in the freezer, but that requires more energy. I can remove even more by using more and more sophisticated scientific equipment, but I can never reduce the temperature to absolute zero. That doesn’t mean the soda in my fridge isn’t colder than one on the counter.

Perfect results aren’t obtainable except in trivial cases.

This whole question rubs me the wrong way, like “Why do we teach women to protect themselves instead of teaching men not to rape?”. There’s not a big control panel somewhere that “society” can use to change everyone’s behavior. People are individuals. Some of them will do bad things to others because it benefits them, no matter what they’re taught. If you want to avoid being victimized, you have to be vigilant against that.