seems to more popular among "developing countries" aka lower IQ populations
I think it's more than that. It's more prevalent amongst those who are lazy, lacking attention, etc. and these people have access to oils and needles.
You would expect the developing countries to be more hardcore, like many of the African bodybuilders---using what they can or building their own equipment.
If Greg Valentino didn't get all that exposure, it would not have grown. And just exhibited certain traits---lazy, lacking attention.