Yea, I can't imagine getting all the safety systems working again in a modern car after a crash.

In older cars it was easy to chop them in two and weld them together however you wanted. But these days with the concepts where the engine compartment and trunk are crush zones and the passenger compartment is rigid so they occupants don't get crushed, there is a ton of non visible damage in even minor impacts.

In order to get a salvage title the car needs to be totaled.

Insurance doesn’t care if there is frame damage. It only cares how much the car is worth, how much it’s going to cost to fix and how much it’s worth at an auction in its current state. They run the numbers and decide if they are fixing or totaling the car.

There is a reason tesla is expensive to insure.

It's also liability. If insurance determines frame damage, they're inclined to often total it and settle with you. You ain't getting that car unless you buy it back. I know this since I've worked in insurance, they don't want to be liable if the car doesn't perform to manufacturers specifications while driving or another accident. Initial repair/value cost is a determining factor yes, but doubly so future liability. Take it to their preferred shop, repair is inadequate, fails to perform while driving = they're liable for way more than initially.