It's because they want you to buy a new car. That's the only reason anyone in their right mind would wait 15,000 miles to change engine oil as well. That is way too long. I have a BMW mechanic who no longer works for the dealer and says to change it every 5,000. It may not be free, but if you plan to keep the car for a long time then maintain it. Worth paying a few bucks in my opinion.