For most contacts you just move away from people who don't use secure communication and may compromise you in the future, no need to convince someone. Works for me.
Those of you who downvoted this comment, please explain your reasons.
E.g. here are mine: not enough people communicate securely right now. I can't just abandon everyone; that's way too isolationist for my personal taste. Still, if you want to that _is_ an option.
people aren't JS libraries, you can't/don't "just move away from them"
"Hi Mom, I just want you to know: I am deprecating our relationship to "acquaintance" because you use Gmail and an iPad"