The one channel nobody can take away
Every other channel is rented. Reach depends on an algorithm, a bid or a policy that can change on a Tuesday. Email is the one list you own outright — and it is usually the one nobody has looked at in a year.
The work is mostly unglamorous: getting the automated sequences right, keeping the list clean, and fixing authentication so mail reaches inboxes. Those three routinely beat any amount of clever copy.