The short answer: "None of your god damn business", which is the point.

The only counterpoint to end-to-end is "we want to be able to access your private conversations", which isn't really a counterpoint unless you agree with spying on citizens and would like to also allow the government to come into your house and place listening devices as they please, listen to your phone calls whenever they please, open up your mail whenever they please, so on. Hell, actually require you to wear a device at all times so all conversations can be recorded. No, just no.