If it was legal to say "If I break this oath, you can fucking shoot me" in a contract, I'd suggest that. The entire point of the exercise is "we promise do the right thing, and to keep us honest we have set up a system by which you can destroy us if we violate that promise".
Corporations can't swear on their life, as they have no life to offer. They can swear on their cash, and by such their ongoing existence.