Bears east & west

I'm preparing for a trip to Whitney and some backpacking in the area. Why is it that the bears (black bears) in CA are able to break into cars & defeat hanging bags so that a bear canister is required for overnight backcountry travel, while in most of the rest of the country, the standard rope over a high branch is good enough and only humans break into cars?

Does anyone have a scientific reason for the difference in bear-behavior? Was it always like this? Do we run the risk of bears in other parts learning these tricks? I suppose that the bears in the Sierra Nevadas taught one another the break-in techniques.