Why do the Rainmaker's henchmen carry guns if murder's impossible?

1. A henchmen would presumably rather be in jail than dead.

Would you willingly let yourself be murdered, if you knew that justice would come to the murderer?
Just because it's likely that the police will find your body after you get shot, does not mean that you would happily be killed by an armed man.

The henchmen would logically carry guns if they suspect that someone (e.g. a rival gang) might try to kill them at one point or another.

2. You can still get away with murder, you're just less likely to succeed.

"It's nearly impossible to dispose of a body in the future. I'm told."

• I'm told - The speaker is not certain about this. He has only been told that this is the case, he does not know it as a fact.
• nearly - Even if the speaker is correct, then it's still not impossible, only nearly impossible (= unlikely).

3. Why focus on carrying guns, and not murder in general?

Why are you asking why people still carry guns, and not why murder still happens? If your argument is based on how impossible it is to get rid of a body, then no one should ever want to try and commit a murder anymore, right?

Except that murder still happens. And that in and of itself can be reason enough to carry a weapon: to stop someone who tries to murder you.

4. Guns are not used exclusively for premeditated murder.

As discussed before, guns can be a deterrent in and of themselves (without ever firing a shot). Gunshots are also not guaranteed to be killshots. And then there's still the argument for justifiable defense.

Not everyone who carries a gun is inherently willing to commit wanton murder.

5. A current example

Criminals tend to avoid killing police officers, because that almost guarantees a citywide manhunt for the killer.

So why do criminals carry guns today, if they wouldn't want to kill police officers anyway?

This is basically the same as your question. And its premise is flawed, because reality clearly disproves your notions. Criminals still carry guns for different reasons (coercing victims, defending against other criminals, deterring people from messing with you), and people in the future still commit murders (which is why the henchmen are armed, to prevent being murdered).

6. Irrational murders exist too.

You're also assuming that all murders are intended and logical. You're excluding many possibilities:

• Committing a murder because of psychological issues (thus not thinking you're doing anything wrong)
• Committing a murder because someone told you it's the right thing to do (e.g. the 72 virgins example that has become a cliché)
• Committing a murder in the heat of the moment (e.g. shooting your husband's mistress)
• Committing a murder, while accepting that you'll get caught (but you want to kill your target anyway)

If you acknowledge than all these murders are still possible; then you must invariably also consider that you might one day be the victim of such a murder. Which means that there's a point to arming yourself: so as to prevent yourself from being murdered.

I think the relevant part of the quote is not what is said, but what isn't.

It's nearly impossible to dispose of a body in the future.

This doesn't mean that murder is now particularly difficult to do.

A lot of criminal organizations in movies are known for making people "disappear". They obviously kill their intended target and dispose of the body, which means there is not any evidence that points to anyone having committed a crime, as it's not even certain that the missing person is actually dead.

However, if the body is ultimately always found, then the police would find any evidence on the body that would point to them as the killer. Even just knowing the identity of the deceased would potentially bring suspicion onto the criminals, if they are known associates/enemies.

It's much easier, then, to literally make their target disappear by sending them back in time, where there is no technology to discover their body from the tracker. No body, no evidence, no crime.

Now, obviously they shoot Old Joe's girlfriend/wife, but she has absolutely no affiliation to their crime organization, therefore the police won't necessarily know that it was them who killed her.

The criminals do make sure to refrain from shooting Joe himself, as he used to be part of the Looper program, so killing him will bring the law a-knocking. They make sure to keep him alive when they send him back, so that nobody in the future knows that he is dead, they will only know that they cannot locate him.

They can still threaten to kill someone. And killing isn't always murder; if they're attacked by other criminals, killing might be in self defense.

As for the tracker, maybe it isn't activated until death?