Earlier quoted context omitted.
That’s part of the issue. But packing a tractor (or car) with electronics and computers does make it inherently harder to work on—even if it’s not locked down.
You need electronics and computers for cost-effective compliance with emissions requirements. Emissions limits have been one of the most positive government policies in my lifetime, saving millions of QALYs. There's lots of other electronics in most modern vehicles, but the public manufacturer rationales for electronic lockdowns almost always point back to emissions concerns because they're so defensible. How do you…
IF we wanted to do it properly, I'd imagine we'd have zero mandatory locks on ECU, just a little closed down black box with sensor installed in relatively tamper-proof way (of course there will always be one, the target is for 90% of people to not bother), logging away and maybe sending check engine light if it detects wrong AFR for too long.
Then you just check that on yearly MOT + any signs of tampering. Then owner is free to tune the engine as they want, provided the exhaust is still within the norms for most of the time.