1. If your business contacts can't take reasonable precautions to protect sensitive information, are they really worth doing business with?
2.
Privacy isn't measured in absolutes. Just because you can't mitigate 100% of threats, doesn't mean you shouldn't take reasonable steps to stay safe. It's kind of like saying don't bother locking your door because someone can still break the window. The more steps you can take, the better.
3. I wouldn't suggest using whatsapp due to their policy on pen registering (they keep a list of who you contact, and when). I wouldn't suggest Skype.
4. There are tons of reasons to want to ensure privacy and confidentiality other than being Pablo Escobar.