I feel like it's not true that their services are end-to-end encrypted. I mean, they are, but they have the encryption keys so it's the same as if they are not.
https://news.ycombinator.com/item?id=29103056 https://encryp.ch/blog/disturbing-facts-about-protonmail/ https://news.ycombinator.com/item?id=17775326 https://news.ycombinator.com/item?id=28057433