Most of us Sumolings use more standard tools and tools purchased through Appsumo, versus a tool for developers. Examples include SendFox, Drip, Mailchimp, Active Campaign, Automizy, WishPond, and my favorite ConvertKit.

Im guessing its because the others don't link well in using your own designed email campaign tools. I use SendGrid right now and it seems they have a starter plan that is free for lifetime (Last I checked) making it much more attractive to a newbie and people testing new products. Just an idea.

If you plan on adding other services please advise timeline. Right now all I see is an investment in this means I will be soon be spending more money before I know what my return on investment will be.