Bigdog, they do come back, IF they are compressed within their designed range. This is a 5 MPH bumper. That means at 5 MPH the car was to have no damage when the bumper struck a solid object. At 6 MPH things start to fail, at 10, good luck.
You know, I have gotten to know some engineers and designers with GM and Toyota and the myths that the look for someway to "sell parts" is simply that, a myth. It is hard enough for them with all the bureaucracy, demands for crash resistance, fuel economy, etc. designing a car, they are WAY too busy for such nonsense.
Honestly, I have had some interesting converstation with them. Such as why don't you make things symmetrical like both left and right bumper bracket being the same to save on production of parts? Every one of these questions is answered very well, there is ALWAYS a reason why the guy working on the car in the shop screaming is WRONG and the designers had no choice or they are simply right and we are wrong.
Interesting stuff.
Brian