So I don't work in automotive domain, but I work in Controls Engineering. Basically everything you just said relates to my work as well, and based on tidbits of anecdotal info I've picked up through various technical forums it sounds like automotive & controls are quite similar in that regard.
The dirty truth is often times these domains were designed and chiefly operated by non-software people. Not to say a mechanical engineer or electrical engineer can't program, it's just that their focus is on their work, and the software is but a tool to accomplish those means. So the world of software has leapfrogged over PLC and automotive design and gone to run laps around it several times since the 90s. It's only in say the last 5 years or so that I've seen a cultural shift in controls towards embracing the modern realities of software, networking, security, version control, databases, etc.etc.etc.
I'm not going to go too much further into this, but this is why Software Engineering as a regulated profession is going to be a necessity as much as civil engineering or electrical engineering has been. The digital world is just too vast and complex now with so many pitfalls for those who only ride the edges can handle. And people's lives are starting to matter. It is no longer safe to treat security as secondary with an "oopsy" anymore. We don't tolerate bridge collapse or electrical design that can destroy livelihoods, why do we still tolerate hacks governing data and safety of public?