The 12v system is to use standard 12v automotive electronics; every electric (and hybrid) car does this. A 12v SLA battery (these cars do tend to use sealed bat

The 12v system is to use standard 12v automotive electronics; every electric (and hybrid) car does this. A 12v SLA battery (these cars do tend to use sealed batteries / AGM with safety vent only) is the cheapest way to provide voltage regulation and power for accessories when the high voltage battery pack is "safed". (Generally, the "start" equivalent for both BEVs and hybrids is a process where the HV battery controller runs multiple safety tests on the high voltage system and then closes relays to connect the HV battery to the rest of the car. This bootstrap process is powered by the 12V SLA battery, since the HV battery is disconnected when "parked" - same reason that the lighting and horn need to run off the 12V battery.) Instead of an alternator, there's a DC-DC buck converter that recharges the SLA battery. SLA is a nice chemistry to use here because it's "self-managing" - you don't need a battery management system for the 12V battery. Tesla has decided to not provide a 120v inverter from the factory. It's not the underlying tech, because other manufacturers do ship inverters and they're a straightforward thing to integrate (as the manufacturer) with the HV battery pack. This is probably about (besides the normal Tesla-being-the-Apple-of-car-companies) battery pack degradation. Tesla currently warranties their battery packs based on mileage, and frequent use as a stationary power bank will put more cycles on the batteries. There is precedent for this - ICE vehicle warranties can be voided for excessive stationary operation. Generally they don't bother for light duty, but medium and heavy duty trucks with PTO have maintenance requirements and warranty terms based on engine running hours as well as mileage.