There is a key area where mail is central: The "I lost my password" feature of websites. Apple ID, Google+ (or whatever they call it now) and Facebook login rep

There is a key area where mail is central: The "I lost my password" feature of websites. Apple ID, Google+ (or whatever they call it now) and Facebook login replace it to some degree (especially on mobile device apps) but for far most websites newly created passwords or activation links are sent via regular mail unprotected.