It isn't a difficult concept. A very small number of people contribute significantly to the network load. Yeah, ideally there's more capacity than anyone can ever use, but back here in reality that would be remarkably expensive to fulfill.
It's the same thing with crime, btw: A very, very small percentage of people are responsible for the overwhelming bulk of crime.
Is there a study that shows this? Intuitively, it makes sense, but I'm curious. Of course, we must be talking about serious crimes, as pretty much everyone breaks some sort of law almost every day.
When other major countries are investing huge amounts in their infrastructures to support higher and higher capacities and bandwidth for lower and lower prices, our ISPs are instead capping bandwidth and increasing prices without investing that higher revenue into better service.
Especially when you pay $25 per GB, and it costs an extra $10 per GB. People will probably stop streaming Pandora over the cell network, and heavily watching movies.
Canada has had data limits the entire time, and Blackberry has been constantly cautioning US providers about offering unlimited data plans in the name of providing better service to their customers.
This kind of limitation for regular ISPs is ridiculous, because the cost of bandwidth is actually cheap, but it's different and much more expensive with cell phone networks.