> You mean, except for criminal law? I don't see how this is in any way equivalent to adding ads to Whatsapp.

It's not against the law to lie to me in most cases, but I still have the same expectation/requirement that people will be honest with me that I do that they won't steal.

Even when doing multi billion dollar deals you would trust a handshake agreement?

I wouldn't trust a handshake agreement on a used car.