SMS messages are often associated with spam or alerts (an ad is not spending enough, or too much, or a landing page is down.)
It’s a typical one-way interaction: we get the alert, and that’s it, nothing much to do. SMS messages can go beyond that.
Let’s say we get a text message saying: “Your Green sushi ad’s CPA is x2 your campaign’s CPA goal. Would you like to pause it? Reply Y/N.”