It really is different for very old classic cars. It warns the buyer that something major has happened to the car. There was a time when a ton of cars from a flooded region were being totaled out, cleaned up and resold. The buyers had no way of knowing the car was a flood car.
Others would take two cars and weld them together, sometimes the job would be sub-par and dangerous.
On an very old car, a simple inspection would reveal problems.
The ins companies will usually only payout 1/2 the value of the car if it has a salvage title
I understand you can get a salvage title for theft recovery or heavy damage. Also, you have to consider the area prices. In California, it's pretty easy to total a car because repair prices are so high.
I had a Honda with a $4400 retail value, got hit in the rear. They wanted to total it out, I argued against it. The fix was a bumper cover and bracket. Cost was about $100.
I think it's setup so the ins companies don't keep paying out on the same car over and over again.
