Email newsletter landing page limits viewer to one action

This above the fold only landing page only allows the user to do one thing: Submit their email. The headline is clever & vague. The sub line gives a bit more info regarding the service: "A free daily newsletter"  and the mock up of the newsletter gives you a peak at what to expect. Morning Brew has a huge following at this point. I would imagine that most signups are now referral based. So they can get away with the vague copy.