You send your well-crafted promotional email blast or newsletter. It has a do-not-reply return address, or it goes to an unattended mailbox.
This is like calling someone on the phone, hollering a sales pitch, and then hanging up before they can buy. (Actually, there are links in the email, so it’s like calling, giving a pitch, saying “call me back at this other number” and then hanging up.)
This is even worse when you realize that the people who reply are your most interested customers! Is that who you want to slam the door on?