Exactly, and cars aren't that hacker friendly. Underneath the design isn't that bad, can-bus makes sense, most modern cars have a good sort of internal network. But there is zero documentation to allow anything aftermarket to plug in later or software to be upgraded past what the manufacturer provides.

And car manufacturers are still very much in a mindset that you make a certain model-year, release it, and then forget about it while you work on the next ones. No upgrade path on software whatsoever.