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 separate them?

Exactly. Electronically controlled unit injectors are expensive--like 10x the price of mechanical ones. They're super cool, they can produce like 10 separate metered injection events per cycle. This is great for efficiency, noise, emissions, etc. But I can rebuild mechanical injectors with a bottle jack pop tester I made from $100 worth of parts and a bench vise. There's no wiring harness, no computer.. If the injector is getting fuel, has decent spray pattern, and is popping at the right pressure I know for certain the fuel system is good. With an electronic common rail system I need some expensive proprietary computer equipment to diagnose it, and there's no way I can build a test bench to rebuild those injectors.