To argue that something clearly wrong is ok because everyone else is doing it is just plain stupid.
In that fashion, ISIS could argue that their torture is ok and necessary because the USA is also doing it to obtain information.
In that fashion, ISIS could argue that their torture is ok and necessary because the USA is also doing it to obtain information.
Edit: I'm referring to spying, not torture.
The only justification for it is "they did it first," which is both childish and irresponsible. Just because everyone else does it, doesn't mean it is correct, necessary, or justified.
It's both an out of band communications channel but also provides a feedback loop. If your enemy or your competitor is engaging in something you all agreed to is out of bounds, you can respond to it with the information you have gained.
EDS and Boeing will know if the other is underselling, bribing, receiving subsidies, etc. and be able to respond accordingly, for example.
See how so many countries are rushing to resolve territorial disputes at the International Court of justice? Only the plaintiffs.