Gmail et al. still add the headers if you send the message through an actual email client though, just not if you send it through the web client. And I'm guessi

Gmail et al. still add the headers if you send the message through an actual email client though, just not if you send it through the web client. And I'm guessing that the vast majority of email users still use email clients at least some of the time, given that they work much better on your phone and they're the easiest way for consumers to have a backup of their email.