In a prior life, I purchased and assisted in the implementation of a vehicle maintenance tracking system for a major U.S. firm.

It is a time-consuming process to both implement and maintain such a system. More to your point, the information value of the data is most important to the owner of the equipment. Each of us owns one, or at most a few vehicles that are effectively the same. There is nothing that is going to be of value to a given shop from gathering the information. You are the one who is going to make purchasing and/or maintenance decisions concerning your vehicle, the shop isn't.

In a fleet situation, the fleet owner can look at say, 100 transmissions or engines or axles of a given model and decide whether or not to buy 20 additional units the following year with the particular component. The maintenance shop may also make decisions about stocking levels of particular parts.

In the case of an individual owning one or a few units, there is no value to be gained from providing you the information. It may well be that the manufacturer is gathering data from their captive dealerships, but that same manufacturer may well have a financial disincentive to publicly publish aggregate data.