Technology

I would also add... the part count hasn't actually dropped overall maybe as much as people might think. Since... seats are parts, head rests are parts, doors are parts, windows are part, body panels are parts, suspension springs are parts. The mechanical drive train part count sure has gone down. There was many many valves and springs in engine and so on. However mostly the overall assembly line is still the same. The final assembly line doesn't care "are we putting in fuel tank or battery pack", "is the motor here electric or combustion one", "oh these fuel lines are electric instead of fluid, well still pretty thick and stiff lines to run, wrangle in there you dastardly high voltage wire as thick as my thumb".

People often forget most of the car... is the car, not it's drivetrain. Drivetrain is there to move around the car, the cabin. Lot of effort and parts go in the cabin and it is often what sells the car, not the drivetrain. Many a car sale is decided on "hey honey, try these seats, these are really comfortable". Instead on "is the 0-60 7.2 seconds or 5.3 seconds". Can you fit the baby stroller in the back boot and so on sells cars. None of that changes, even though the mechanical drive train is completely different.

All the upholstery and final assembly department is still exactly same. Except the fuel tank and engine reverse weight. The electric motor weights less than the engine block, but that electric fuel tank sure has gained weight over the empty liquid one.