Plus, isn't the claim literally that there is correlational evidence here? That lightly suggests your model of how the world works in this area is off.
It isn't like they are bugging people, its more like they overhear a conversation or see something of interest and find a way to jump in, in a way that isn't intrusive. "I can't help having overheard, but are you planning to open a Taco truck on 5th?" That kind of thing.
And yes, i don't do any networking at all, literally never met any person i did business with, in 25 years of career.
Or maybe, that is my European perspective? Because i probably never seen people doing that. There is an old observation that "networking" is American only cultural phenomenon and it doesn't exist in Europe - maybe it's one of the ways it manifests itself?