Automotive manufacturers have a massive markup on the next "trim level" that includes these creature comfort items.
They want to make sure their dealers and customers can't just buy the optional parts from a wreck to upgrade and make the vehicle more valuable.
This kinda stuff plays into the edges of the "right to repair" movement.
GM charges an insane amount for Global architecture control modules. Ford, Chrysler, Toyota, ... are playing the same game. They've purposely made it almost impossible to install a perfectly good used replacement module ( It can be done but it's not easy ). The reasons are twofold. They make extortionate profits from the sale of these controllers and the price of these parts makes the cost of repairs high enough that scrapping the vehicle and buying a different one is attractive. That is the goal. Planned obsolescence. Just like appliances but they actually have to skirt better consumer protection laws than the appliance industry.
Their argument is they want to keep the internal software out of the hands of competitors. Smoke and mirrors boys. Any electrical engineer worth his salt can reverse engineer one of these controllers and build one that doesn't infringe on the originators patents in a fairly short timeframe.