The cars today are using more electronics than some homes used 50 years ago. The computer is much more advanced than the space shuttle used. But yet they are functioning on 12 volts.
They at one time we’re going to add more than one battery or more bolts but other than a couple cars they chose to remain with a 12 volt system.
I am not sure if you have experienced this but should your battery begin to fail the body control module in most vehicles will begin to control and shut down systems in the vehicle and Chanel power to specific parts to keep the car running.
I had car with a battery that was failing. I jumped started it and told my wife to take it home. As she drove the HVAC shut down. Next the radio shut down. Next the dash and speedometer shut down. The power was all sent to keep the car running and power steering working.
You can be sure the power seats and heated wheel was already disabled.
That was 04 you can be sure todays cars with the more advanced electrical architecture is even more advanced.
Chips and processors are key to all this power management.
Note too these systems while helping keep the cars on 12 volts also will make them more efficient when they go all electric. This way power will be managed efficiently and not cut into the range as much or in cold weather it will be more effectively used.
There is a lot more going in than many realize anymore.