"I remember the time I wanted to see the service manual, and it took a wink and a nod to get the service tech to decrypt it for me."
Boeing and Airbus are incredibly protective of intellectual property for both safety reasons and protecting the process. They still provide repair manuals.
There are hundreds of sensors on modern John Deere tractors they REQUIRE the entire firmware to its respective module because they are locked to your serial number, that means you could buy two identical tractors and swap a part between them and both tractors would cease to operate correctly because the module rejects the non-programmed sensor, this is unacceptable.
Now you might say well John Deere has rights to protect its own IP to which I absolutely agree, and I also agree they have the right to protect themselves from liability arisen from say someone installing an aftermarket sensor. Why not make a disclaimer appear saying "This equipment is fitted with a non-certified aftermarket part) rather than making it completely useless "contact dealer" is not a valid diagnostic message.
Let's say you wanted to hack your tractor to install an aftermarket sensor, well now you have to break the digital lock (encrypted payload files) that is installed by John Deere congratulations that's actually against the law even if you own the equipment.
This isn't about emissions or safety or anything else it's about shitty rent-seeking behavior that directly disenfranchises everyone.
When you purchase something, you should be able to own it.