The reason is better oil. Many European engine makers have specifications for oil just for their engines. They don't use much "generic" oil like API-SM. The oil is usually synthetic, and usually good for 10,000 miles between oil changes, sometimes up to 18,000 miles. The European consumers would never consider wasting their time getting oil changes every 3000 miles, nor dumping that much oil to be recycled. They want once yearly engine maintenance, including a yearly oil change. They are using lighter viscosity oils, 5W-30 in cars and 10W-30 in diesels, in their push for lower fuel consumption. If I can make a very broad generalization, Europeans want more value for their money, and want assets for the very long haul. Americans want for quantity for their money and rarely care about quality above the minimum. They want new assets frequently. (I know, many, many exceptions.)
Ken