Why did they put a plug in with such high voltage, that can't even run a rice cooker?
I suspect the reason is so people can charge their electronic gadgets, particularly laptops, easily.
Laptop charging was until recently, a mess of different connectors (some standard some proprietary) and proprietary methods of signalling to the laptop how much power the supply could deliver. "Car chargers" running of 12V did exist, both units specific to one manufacturers charging system, and "Universal" units with a bunch of interchangeable tips, one of which might suit your laptop but they weren't something most people owned and unless you made careful comparisons beforehand it was far from gauranteed that a "universal" charger would work with any particular laptop.
In recent years, USB C has helped improve the situation but it's still far from ideal. USB C has many different modes voltage/current combinations. Virtually any USB charging port will charge a phone or tablet (though sometimes slowly), but laptops tend to be fussier about what modes they will accept. A basic USB C cable will only support up to 60W (20V 3A), higher power modes require special "electronically marked" cables. There are also still many laptops in use that don't support USB C charging.
All this is to say that often the easiest way to charge a laptop in a car was and to some extent still is, to use an inverter to step the cars voltage up to "mains" and then to use the power supply that came with the laptop to step that back down to what the laptop wants. Still a separate inverter, and a heavy cord to power it
An obvious way to make this even easier and more convenient for customers is to integrate the inverter in the vehicle. Then people can just plug in their laptop without buying any special stuff.
Larger inverters absolutely do exist, but they cost more, take up more space and require heavier cables to supply them (and connect them to the outlet if the outlet is not part of the inverter). Use of a larger inverter may also require installing larger batteries and a larger alternator to avoid problems with draining the batteries and/or it may require keeping the engine running while using the electrical equipment.
Ultimately, auto vendors have to tread a fine line between providing the features customers want and keeping the cost and fuel-economy of their vehicles in check.
Some EVs now support "vehicle to load", a special adapter is plugged into the charge point on the car, and the charge circuit in the car reconfigures itself as an inverter. This allows high power to be delivered cheaply because it's reusing mostly the same electronics as charging the car, and because the batteries operate at a much higher voltage.