> The main reason is that it's the only traffic that you own. It's not at the mercy of someone else's algorithm.
You are at the mercy of Gmail/Outlook's spam filtering algorithms
You are at the mercy of Gmail/Outlook's spam filtering algorithms
On Twitter/Instagram/whatever, you're exposed to the arbitrary censorship choices of the platform AND the risk of being deplatformed for any reason. Once that happens, you don't just lose deliverability, you lose every single relationship you had.
With an email list, at least you retain the list should your deliverability tank. It might take a lot of work to migrate to a new non-deny-listed setup, but at least you have a (hopefully double-)opted-in relationship with each prior reader still.