It is in many fields. They're Professional Engineers, and they build nearly everything that's important to a society. Software is overrun by literally anyone and everyone because it's not a protected field of engineering
Hang on, my understanding of the situation is that only PEs are allowed to sign off on the design of a thing. They don't have to design it, and they almost certainly don't build it. Am I wrong?
The stamp is legally binding. The company you work for isn't gonna protect you financially if the bridge you stamped falls. This is how they protect their profession