The vast majority of people are not able to run a mail server. Of the ones that do some should not be doing it because they're not clueful enough to keep it secure and out of blocklists.

> Can't you just use pgp encryption and it doesn't matter where your email is stored.

Most people get freaked out by context menus and right-clicking. You're smart; you're surrounded by smart people; you're surrounded by people who know computers. I think you might be unaware of just how bad most people are with computers.