I agree - The cost of the oil itself and the filter is minimal. It's the moron they hire to change it who leaves the drain plug loose, or under or over tightens the filter (or neglects to change it at all) or leaves the oil filler cap off the engine
The more often you need to have someone work on your car, the higher the probability one of them will screw something up
True story - My daughter took her car to the dealer for an oil and filter change and they left the filler cap off. About the time she got home and shut the car off, she noticed smoke rolling out from under the hood. A check showed she was a quart low. Then, the dealer had to keep the car two days to steam clean everything. Better I guess than the finger tight drain plug stories I've heard so many times where all the oil runs out
I think the manufacturers realize that if your first service isn't due until after the warranty expires, there's much less chance one of their 'technicians' will screw something up which would require a new engine under warranty!
Don