Similar to in many courts of law;
A conviction is generally characterized by the analysis of two main elements.
The actus reas: The guilty act
The mens rea: The guilty mind.
When looking at luring: The subject (victim) may not be aware of certain game mechanics, which in turn is their fault and may eventually put them at some sort of loss at some point. This isn't essential information because the focus for this situation is on the offender (lurer). Performing a lure is a very premeditated and planned attack with an effort to steal someone's goods; whether or not the victim is educated on how the mechanics work, the lurer has a clean intention to tactfully steal their goods.
Why wouldn't luring be a perm-bannable offensive if it's such a premeditated and though-out form of scamming? It's probably one of the dirtiest forms of scamming out there in my personal opinion.
What makes it worse is that normally a lot of social engineering is involved to build up to the scene of the crime. A lot of the time it comes at the cost of compromising a good friendship.
Game mechanics are game mechanics, they'll always be manipulated. The same way that users used to pull items out of trade boxes near the last second of the first confirmation screen to swap them out for cheaper items. From an unconfirmed source I heard that accounts were monitored that were frequently reported for "scamming", and when they performed this action under the presence of a J-mod, they were banned for the offense. Jagex later implemented several security updates for the way that the trade mechanics worked, however users were punished for manipulating it in the past.