During last week’s MoffettNathanson conference, Bob Iger teased one of the ways that Disney plans to succeed at streaming: “Every time they open the app it has to be something different—this is where A.I. will just be a huge, huge, important tool to do all this.” No disrespect to Iger; he’s talking about A.I. personalization and password-sharing crackdowns and integrating Hulu into Disney+—all fine initiatives, and all being adopted across the industry. But Disney’s streaming services are so far behind Netflix on pretty basic tech issues. They don’t even do the one thing that could instantly increase engagement and reduce churn: video previews.