The logic that they have different social conditions that place different incentives on people's behaviour. For example, Venezuela banned private gun ownership, but that is not the reason for firearm deaths falling. The reason for that is because of the economic meltdown is so bad that bullets are too expensive for even criminals:

* https://www.independent.co.uk/news/world/americas/venezuela-...

It is a control on the variables that can confound comparison so we have a more apples-to-applies situation.