What puzzles me is that more people don't go with a 5000 mile interval, since it's easier to remember on your odometer.
In Canada, the 3k oil change is easier for most people to remember simply because our odometers are in kilometers, and 3k is roughly 5000km. Although I still think a lot of people up here should just be going with a 10,000km interval (6200mi) for simplicity.