I'd love to see any data at all about this. Or even a few not cherry picked examples.
You also wrote: "The electric plug situation is rapidly improving".
I have seen zero evidence for this. I've yet to travel to any other continent without this being a problem.
Anyways, as little as 20 years ago, you'd routinely need adapters when traveling from one European country to the next. That's hardly an issue anymore, and I consider this a vast improvement.
You say you have problems when traveling to "other continents", without saying which continent you start from. I'll assume you're from North America, because then you're indeed a bit out of luck, as this map shows: http://upload.wikimedia.org/wikipedia/commons/d/d7/WorldMap_... However, that's a North American problem, not an international one.
As to your other point, I didn't cherry pick the examples, I addressed the examples from an article that argues the exact opposite.