Why Automation Does not have crash physics like official BeamNG Cars & other MODS outside Automation?
Automation is a really complex game that allows the players to design basically anything in terms of cars, so it needed a universal exporter to be able to export anything the players make to BeamNG, regardless of what mods they use and stuff. So the exported physics have to be universal to work for any Automation car and it means that they can't be adjusted for a specific car because that would mean they wouldn't work properly for any other car. At least be thankful that if you make a reasonable car it won't explode, they really did an amazing job on the exporter to make it as stable as possible. Another reason is because in Automation you can't specify where exactly your car has the doors, hood, trunk, etc. Or even how many doors it has and how should they open. So BeamNG treats it as if it had no doors or anything like that to avoid weird glitches.
Because the body shape is registered as one whole shape, which means that things like the bumper can't get broken off. Also the node placement is very simplified.