One thing to note is that companies like Toyota actually do specify 6-months/5,000-mile oil changes. It's that they always have two schedules, one for cars that do mostly highway miles in warm weather, and another for stop-n-go traffic, winter, towing, and any other type of driving that's harder on the engine than cruising along a highway.
The problem is nobody goes by the actual recommendation. They see the longer oil change interval and go by that regardless of how and where they drive.
And again, even going by yearly oil changes the engine will last what most people consider the life of the vehicle, around 10 to 15 years or around 150,000 to 180,000 miles.