If it was really that thick plate it would be, but making any modern vehicle (that’s not meant for military use in hostile territory) out of thick plate is fucking stupid. And keeping thin stainless flat is really tricky, it wants to have at least a bit of curve to stay rigid. It asoc doesn’t like consistent forming, which is why nobody since Delorean has bothered.
Both for weight, and economy, but also for accident safety—good luck of you’re not also in an armored car, and occupant safety, since the crumble zones are greatly reduced and going to transfer way more energy into your soft tissues and internal organs.
But you can throw a rubber baseball at it just fine at least.
Or the professor who’s profiting off requiring the latest edition of their own book each year.