Maybe IoT garbage can ship with just about any chip that will run Linux, while cars need specifically certified components?
* https://en.wikipedia.org/wiki/Automotive_Safety_Integrity_Le...
https://www.st.com/content/st_com/en/about/quality-and-relia...
It's not about laziness, it's about certainty, certifications, and saving money on unnecessary redevelopment and testing. If each of the ICs on your board gets discontinued every two years, and you have 20 ICs on your board, it means that you will have to go through redesign and re-testing as often as you buy components, even if you're doing ten batches a year.
But for example, an ESP8266 hasn't really lost much value in the past few years, and is unlikely to lose significant value if it sat on a shelf for another few years, so they don't mind a bit of an overstock.
Meanwhile the current year car model will lose a ton of it's value when the next model comes out so they don't want to risk over-stocking it.
But if you've got loads of chips on different boards from different suppliers, a structure suitable for a large business, lengthy supply chains, complex certification requirements, and you can't afford to pay much more? Well, that's going to make things quite a bit more difficult :)