It is not that clear cut. Stamping requires softer steel which can be bent in those stamping machines. However, softer steel kind of goes against the purpose of

It is not that clear cut. Stamping requires softer steel which can be bent in those stamping machines. However, softer steel kind of goes against the purpose of of the body parts in the car. If you use softer steel you need more of it to ensure it carries the weight of the car and handles the stress the car is expected to take without deformation. Existing cars and trucks probably carry a lot of extra weight just so that they can use that soft bendable steel. There is another benefit to softer steel in that it absorbs vibrations. But this is less relevant for electric cars, because there are no vibrations form an ICE. Furthermore, stainless steel is too hard to be used for stamping machines, so if you use stamping you have to worry about rust. So it is very possible that the Tesla engineers did the math and figured out that if the body did not need to absorb engine vibrations, they could save a lot of weight and ultimately energy if they used casting.