The main reason car makers don't specifically recommend high end car care is because they would prefer you buy a new vehicle every 3-5 years rather than maintain your current vehicle. For example, synthetic oils were known to improve fuel economy, engine life, and with less environmental impact for at least 20 years before they were factory filled and recommended on anything other than sports cars.
Also, while at SEMA at least two buyers approached us asking us to submit a bid to fill their factory labeled car care line...so you never really know what you're getting in the bottle from the parts counter. All you know is that it meets their requirements for the price they wanted to pay. Same goes for their oil, filters, and other maintenance items. I'm not saying its a bad thing, but dealer and manual suggestions are usually not cutting edge and are geared much more toward profitability that what's best for you/your car.
One last point, we should be careful not to infer that manufacturers recommend against coatings just because they omit them from the manual. Our coatings will not void or limit the manufacturers paint warranty in any way...but, polishing away more than a few microns will with some manufacturers. So, another question may be whether or not we have already accepted a detailing practice that should be performed much less often and with less aggression.