Great subject and thoughts!
*Oil changes= most every shop I know does an included complete digital inspection these days. It's much an expected "complimentary" thing to most customers, including those who go to dealers. Dealers around my area have the greatest prices and convenience with no appointments necessary for the most part. Even though oil change services are finally going up in price noticably, it would be more challenging to charge and justify to customer the reasons why we might charge more for a created "service". They might even agree, but they would rather spend less money. I think most of us would, too (especially if we fairly relate it to some other non automotive professional service we might use). Sometimes we recommend a "6 month inspection" , separate from an oil change, mainly to check the battery, wipers, tires, lights. Many times on vehicles which have low annual mileage accumulated. Battery is the biggest concern usually.
*Transmission oil changes= I often wonder how much difference it really makes in longevity of many vehicles' transmissions; it seems like some designs just inherently have issues no matter what, and some last forever if you never change the fluid. Some shops will not risk changing fluid if it is dark, with fear a perfectly good working transmission will develop an issue after service, and the vehicle all of a sudden becomes an undrivable "mechanical total loss". Most of us have seen that happen.