To ensure that the update process finishes without interruption due to weak battery - if that happens it can brick your car. Tbf you can also just connect the battery to a power source and keep the engine off. Depending on update and car updates that take a few hours are not unheard of
iirc some mushrooms do that without the corpse - the main mushroom is in the center underground, while the fairy ring is basically the fruit it produces (these are probably not the correct words to describe this - but thats the principle, I think :D)