Don't forget about the size of components such as alternators and starter motors etc. Modern ones that are very high output are incredibly small compared to the old clunkers. Really important for packaging.
We have to power all the mod cons like heated seats, power windows, power tailgates, multiple entertainment systems, electric power steering, electric HVAC, dynamic suspension systems, air suspension using electric compressors, seat belt pretensioners, electric brake assist, really powerful ignition systems etc etc.
Modern cars have many computers in them as well now.
lt all really adds up.
You're also correct about weight. A wiring loom in a modern car is surprisingly heavy. The more they can use higher voltages and tech like CANBUS helps them reduce weight .
