My dog has absolutely no interest in this.
I'd like to ask those with the problem two questions to see if my guess is right:
1. do the dogs that do this, eat a mainly kibble diet? Or is there any other common diet factor here.
2. how much challenge and use to these get for their noses.
Dogs are very quick to spot something that rewarded them and repeat the behaviour.
I'd guess this starts with getting a kick out of an unusual smell or taste.
Once learnt this will be harder to stop than if it never starts of course.