You can give out this advice, very few people will follow it. Given the choice between giving up some privacy and the convenient of sending an email to a friend

You can give out this advice, very few people will follow it. Given the choice between giving up some privacy and the convenient of sending an email to a friend or colleague using gmail, the vast majority of people will choose the latter. Meaningful improvements to privacy must come with negligable convenience tradeoffs if you want people to actually adopt them.