Murder takes physical effort. Stealing something you already have in your posession does not take any extra physical effort. Don’t conflate the two. You may also be completely ignoring some of the work people have done studying self check outs. My understanding is that people who would never think to hide items from an actual checker are much more likely to leave items unscanned. And that many of them justify the behavior in various ways.

I think petty theft is far more instinctive than you may realize. I personally have to fight the urge to steal my daughter’s holloween candy, even though I can easily afford my own, and she would give me some if I just asked. I don’t know where the urge comes from but I know it’s there, and I doubt it’s an uncommon type of urge.

Social interactions can really help to bolster behaviors we prefer in ourselves. I can see them being useful in keeping honest people honest. In the same way a gym buddy makes it harder to skip a workout.

There certainly would be more murders if concrete deterrents were relaxed or eliminated. We definitely do not rely on the honor system to keep murder rates in check.

In any case, someone raising questions about emergent behavior in the general population shouldn't invite questions about that specific person's imminent ethical lapse.

It is not, and I think that is because it is generally rational to not murder or steal. I think irrationally following your conscience wears you down.

You clearly have not worked retail.

Murdering people has a totally different risk/reward situation than petty theft. Additionally, situations where murdering someone confers a benefit on the murderer are much rarer than situations where petty theft confers some benefit to the thief.

Heck I would have murdered a few by now if murder was legal.