Takes time and money. Writing code, developing tools, and creating repair manuals has to be done either way.
How in gods name is making something accessible more expensive when you are already doing these things for your internal technicians.
There is a great deal of encryption on modern vehicles; most new models have encrypted communications backbones.
>"Takes time and money. Writing code, developing tools, and creating repair manuals has to be done either way."
What takes time and money? Obfuscation, or creating open tools? I think you may be surprised to learn how poorly the 'design-side' supports the 'service-side' in automotive and other vehicular industries.
>"How in gods name is making something accessible more expensive when you are already doing these things for your internal technicians."
The automakers do a lot of ad-hoc stuff, and they're often inconsistent between models and platforms. Making things uniformly accessible is different from their normal modus operandi, and likely more expensive.