Your email list is the only thing you truly own.
Despite how much time we all spend building our following on social, none of us own that audience. If Facebook, Instagram, LinkedIn, Twitter, or Snapchat decide to shut down their platforms, they’d be shutting down your audience right along with it. Likewise, you’re always at the mercy of a particular platform’s algorithm. When it changes (and boy, does it ever change frequently!), you’ve got to continually find ways to work with the algorithm to get back in front of “your” people.
With email, that list is YOURS. You own it. Should anything happen to your email platform or you decide to switch providers, you just download your list and sleep tight knowing that your audience is still perfectly intact, and waiting to hear from you.